Hello Niccolo,
Recovery of a deleted storage account is not guaranteed. Recovery is a best-effort attempt. Microsoft recommends locking resources to prevent accidental account deletion.
If the storage account that you want to recover is not in the dropdown/list in the portal, then it cannot be recovered.
For more information kindly check Recover a deleted account from the Azure portal.
Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
If you have any other questions or are still running into more issues, let me know in the "comments" and I would be happy to help you.