If you delete the Bitkey app from your phone, you will need to go through the recovery process to restore your Bitkey wallet. The recovery process can be started quickly by restoring from your cloud backup (by connecting to the same cloud account you used when first setting up your wallet or accepting the invitation to be a Trusted Contact) or by replacing your mobile key using Delay + Notify. See Recovery for more information.
Note: If you are a Trusted Contact for a Bitkey wallet and only have the Bitkey app (without the Bitkey hardware device), you will lose your Trusted Contact credentials if you're unable to recover from the cloud. In this case, you'll need to be re-invited by the wallet owner to become their Trusted Contact again.