Definitely ask staff. I have heard of only one case in which staff typically do something like this; when they find a user under 13-years-old. Regardless of the reason, I would have thought there should be some log entry.
I know there is no log entry, that is what I found unusual. Even if staff removed the user's contributions, I would at least expect an entry saying which staff removed it. Of course, it would defeat the purpose of it included the username but at least you would know who to ask about it.