and found out he had somehow changed the user name and pw on the account
When I hear such stories about "somehow" changing username/password, I tend to think it doesn't hold water. I feel that either you screw something up in the system or don't exactly know how to login to the system or how it works. There are very little chances someone could just change this information. I assume the one who could login (you) could have changed it too - so why didn't you change it right after you logged in..