I am pretty sure the ability to do this has been completely blocked using any available legit actions in order to prevent you from stalking your ex - lol. That was exactly the behavior that caused IMVU to change the way room searches worked. As mentioned, you used to be able to put the avatar name into the room search and it would also return a hit on anyone with that name in found in a room. That has been 'fixed'.
BTW, I used to know creators who used that functionality to find people who had bought their products to go and thank them personally. A lot of users found that creepy - go figure.
For the time being, I don't think even TIM's mad scientists have been able to find a way around the fix
