Is there a location on the forums for people to list lost items? I have already checked with out hotel.
From the Policies page (Gen Con | Policies and Show Information)
"LOST AND FOUNDThe Gen Con Show Office will serve as the center for lost and found items during the convention. Unclaimed property will be turned over to the convention center security office at the close of the convention. You can help protect your belongings by including identification tags with mobile phone numbers in wallets, purses, backpacks and other loose items. Labeling belongings helps us attempt to return recovered items to their rightful owners."
You need to contact the ICC and hope: A) It was turned in to Con L&F and B) the ICC hasn't thrown it away after a month.
Other than that, the General Info forum and here are your best bets.