Hey there! Nice to meet you!
Based on your description and since you were suddenly signed out of your account, your Microsoft account was compromised. The hacker was able to remove the account's primary email address/security info and replace it with their own email address, which is why you received the error that your account doesn't exist when signing in.
Since the security info has been replaced by the hacker, I'm afraid there is no other working method to recover the Microsoft account, and Microsoft Support cannot help either.
Also, since you mentioned that your email is an Outlook account (a Microsoft domain) that was removed by the hacker, unfortunately, it cannot be associated with any Microsoft account again, as stated in this article, particularly under the "Remove an email address" section: https://support.microsoft.com/Outlook/add-or-remove-an-email-alias-in-outlook-com
Thank you for your understanding.
Best regards,
Darhyl