You lost the device holding a Google passkey

A passkey can be stored on a device, security key or synchronized provider. Losing a phone does not always mean losing the account, but the recovery route depends on where the passkey lived and what other methods are available. Anyone who can unlock a lost device may also be able to use a passkey on it, so act promptly.

Recover and reduce exposure​

1. From a trusted device, open the normal Google sign-in page. If the missing passkey is offered, choose Try another way and use an existing password, another passkey or a recovery method. Do not enter account details into a link from a stranger offering “passkey recovery.”
2. Once signed in, review the account's passkey list and remove the passkey associated with the lost or stolen device. Also inspect signed-in devices and end sessions that should no longer be trusted.
3. If the device was lost, use the platform's find or lock feature where available and secure your mobile number and recovery email. A removed passkey is only one part of securing the device and account.
4. Create or verify a replacement sign-in method on a device you control, then perform a normal sign-in test. Keep recovery codes or another factor accessible without the original device.

What Google says​

Google's passkey help documents Try another way, removal after device loss and the fact that adding a passkey does not remove existing recovery factors. A synced passkey may reappear through the provider after you regain access to that provider, while a hardware-key passkey depends on the physical key. Do not assume the same recovery path for every service; check each important account's options in advance.