I recently encountered an issue with Azure Active Directory (AD) where the users I added disappeared unexpectedly. Here’s the detailed scenario:

I added a couple of accounts to my Azure AD and assigned them the appropriate roles.
I double-checked to ensure the users were there and had the correct permissions.
I informed my clients to expect an email invitation to join the directory, but they reported not receiving any emails.
When I returned to Azure AD to investigate, I found that the users I had added were no longer present.
My questions are:

Are there any known cases where users in Azure AD might get deleted automatically?
Does Azure AD have a time-bound feature where if users do not accept the invitation within a certain period, their accounts get removed?
I would appreciate any insights or suggestions on how to prevent this issue from happening again.

Thank you!