01The direct answer
They are fine. Your assets are recorded on the blockchain, not inside that handset. With the phone gone, as long as your seed phrase backup exists you can restore the same wallet on any new device with the balance untouched.
What a wallet app stores is an encrypted copy of the key and an interface. Device gone, copy gone — but the words that generate the key are on your paper, and they rebuild the whole wallet. The derivation is a public standard, so any wallet implementing it can do this.
The good news carries a condition, and the condition is the point of the article: you have to actually have that backup. If the seed phrase existed only inside that phone, then losing the phone and losing the assets are the same event.
02What to do, in order
Assume the device is in someone else's hands and act accordingly: lock or wipe it remotely, change the passwords on connected accounts, then restore the wallet on a new device and move the assets to a fresh address.
- Remotely lock or erase the device using the manufacturer's find-my-device service. This alone stops the majority of "someone picked it up and had a look" cases.
- Change the passwords on connected accounts, especially email and cloud, since those are the reset path for everything else.
- Replace the SIM. SMS codes are the last line for many accounts; get the old number deactivated quickly.
- Restore the wallet on a new device from the seed phrase, and confirm the assets are there.
- If you suspect the device was unlocked, move the assets to a newly generated wallet address rather than continuing with the old one. Reasons in the next section.
- Handle exchange accounts separately: sign in, terminate every other session, check the withdrawal address whitelist, and reset two-factor if needed.
If what you lost was a phone with an exchange app
Different logic, worth separating. An exchange account does not depend on a seed phrase but on a password plus verification methods, so the race is about who controls the account first:
- Sign in from another device immediately and terminate all other sessions.
- Change the account password and the password of the linked email.
- Check the withdrawal whitelist for addresses you do not recognise.
- If the authenticator app lived on that phone, rebuild it on a new device from the backup key you saved. Without one, use the platform's reset process, which normally imposes a waiting period.
The good news on this side is that there is someone to ask: platforms have support and risk teams and can freeze an account showing anomalies. Which happens to be exactly where the custodial model earns its keep — the trade-off is set out in Web3 wallet vs exchange account.
03When it is genuinely dangerous
The danger is not "the phone is gone". It is "the seed phrase was also on the phone", or "the wallet was unlocked and the password was weak". The first is fatal; the second gives you a window.
- The phrase was on the phone as a photo, screenshot or note: the worst case. Anyone who unlocks the device gets everything, and switching devices does not help, because the words themselves are exposed. The only action is moving the assets to a completely new wallet immediately.
- The wallet app had its own password or biometric lock: the attacker must clear the phone and then the wallet, which gives you time to move funds first.
- The phrase lives only on paper: comparatively safe. At worst they reach whatever was already unlocked on that device, and you can get ahead of them.
- The phone merely broke and nobody else has it: essentially no risk; restore from the phrase.
"Losing the phone barely matters" and "losing the seed phrase ends it" are two faces of one sentence. Devices are replaceable, words are not. So the thing genuinely worth your attention is not adding another lock to your phone — it is where that piece of paper lives and whether a second copy exists. Standards in seed phrases and private keys; audit it with the seed backup self-check.
04Migrating a wallet to a new phone
Do not use a full-device backup or an app data transfer to move a wallet. Install the wallet fresh on the new phone, restore from the seed phrase, verify, and only then wipe the old device.
Why avoid device migration? Because it copies the wallet's encrypted data along with everything else, passing through cloud storage or a transfer channel and adding a link you cannot audit. Restoring from a seed phrase is the path this system was designed around: clean and reliable.
The order:
- Confirm you hold the correct backup — ideally check it against the old phone while it still works.
- Install the wallet on the new phone from an official channel.
- Choose restore or import, and enter the phrase.
- Verify the address and balance match the old device. A different address usually means a different derivation path setting, changeable in settings — do not assume the coins are gone.
- Run a full receive-and-send test on the new phone.
- Only then wipe the old device, and confirm nothing seed-related remains in its photos, notes or cloud storage.
Moving the authenticator across
This is where phone changes most often go wrong, because unlike a wallet there is no phrase to fall back on. Those six-digit codes derive from a secret generated when you first added the account; if the secret does not travel, the codes never match again.
Two workable routes, and both require the old phone to still be working:
- Use the authenticator's own migration feature to export entries to the new device. Most mainstream apps have one.
- Re-add each account using the backup key you saved when enabling two-factor — which is why that key should have been written down offline at the time.
If neither happened and the old phone is gone, you are left with each platform's reset process: submit identity documents, wait for review, and expect withdrawals to be restricted meanwhile. Tedious, but at least that road exists — on the wallet side, it does not.
Related security settings are in section 04 of the exchange sign-up guide.