Most Helpful Guy
The search functionality on here is pretty poor. The best way is actually just to go to google and type "GirlsAskGuys " and then his username. That will likely bring up results in which he has posted and then you can get the link to his profile.
Most Helpful Girl
If you can remember a question they had asked on here you could try searching that question and find their profile that way that's what I done because this site wouldn't let me look for the profile itself