It is important to keep your secret phrase (24 words) backed up at all times. Even if your phone gets lost or stolen, you can use the phrase to import your wallet on another device. Recovering a wallet is done solely with the secret phrase. This is not saved anywhere in the system, you were the only one who had access to it. If you don’t write it down or never create a backup in iCloud/Google Drive, you will not be able to access that wallet anymore.