I am not a laywer, but this is in the "Terms of Use" that we hit "accept" too each time we log in:
"You may not sell or auction any Game accounts, characters, items, currency or copyrighted material for real-world money or items or services of any value"
So it is, not that you shouldnt be warn first. Glad your account is back! I would suggest just moving along and let a sleeping dog lay... So, true so didnt sell, but you did supply into the business model and it would be considered part of an auction, Thus breaking the "terms of use".
You should be buy gold from me anyway, you can't trust those other farmers!