I copied and pasted the name they sent to me through email. They did say they hadn't been on here in about 6 months until recently.
I never saw a post of theirs to go back to...
Don't worry about it: I'm thinking they gave me the wrong name or something.
Did the advanced search and search by username option. No luck. Unless the user gave me a completely wrong name, which I copied and pasted from their email, then I guess i am out of luck.