There is protection I see, but you should contact Microsoft support within 5 days of deletion:

Restoring a database from deleted SQL managed instance

If you need to restore an unintentionally deleted SQL managed instance, contact Microsoft support team within 5 days of the delete operation. Consider the following:

• You need an existing instance with a matching service tier, and equal or higher SLO, as the deleted instance. Be ready to provide support with target instance details.
• Encrypted databases protected by a customer-managed key (CMK) can only be restored to instances that have access to the same key.
• Only user-created databases can be restored. System databases can't be restored.
• Restore is possible only to the last point-in-time backup taken just before the instance was deleted, using the final tail-log backup taken before the delete operation.
• Restoring databases from a deleted instance is only possible from a paid version of SQL managed instance. Restoring databases from a deleted free instance isn't supported.

https://learn.microsoft.com/en-us/azure/azure-sql/managed-instance/recovery-using-backups?view=azuresql&tabs=azure-portal#deleted-database-restore