user account disapeared elgg 1.7

I have just been notified by a user that they cant login to their account on an elgg 1.7.22 site, after logging in as the site admin I searched for the user and cant find a them at all on the site. I'm confused on whats happened to this users account.

There is no way they could have deleated their own account as there is no such function on the site.