There is an audit trail in NPM that can tell you. If you go into the website and go into the Message Center, you can deselect everything except Audit Events, then filter those by User Deleted.
Change the Time Period accordingly and then Apply and you should be able to find out who deleted it. Unless it was an AD account that was only logging in due to an AD group it was tied to that it may no longer be a member of.
THANK YOU!!!!! I was able to find exactly what I needed!