log-in user no longer there

I'm writing in for my boss, so I may not know the whole situation.
When turning on the laptop, there are supposed to be two users, him and his
wife. However, about 2 weeks ago (at least) when he turned it on only his
wife's icon was there to click on. I know neither of them have password
protection on the accounts. Where did his user go and how do we get it back?
Thanks!