Can I sue a fantasy football commissioner for not giving league champion the winnings?

Probably. In all likelihood, an oral contract existed among the people who played in your fantasy football league, and in Virginia, oral contracts are legally binding. If the leage commissioner was holding the cash until the winner or winners were determined, he or she would be obligated to make payment pursuant to the agreed-upon terms for your league's winner distributions. Furthermore, if electronic communications were sent regarding the winnings or distributions, those may be used as proof of the contract. If the league commissioner has gone MIA, however, that could mean you would incur additional costs in starting a lawsuit. Since you would be required to provide legal service of process on the comissioner, it cost you additional money and time to track him or her down. This wouldn't affect the validity of your claim, but it might impact whether it's worth your time and money to pursue it in Court.