Was the snapshot taken yet? I've searched a bit and I found some results about it being postponed. So if that's the case, you can simply withdraw the funds to one of the exchanges that are going to support the airdrop, and wait until they distribute XYM to their users.
Yeah I know that it has been postponed but a clarification from Bittrex would still be nice. But at latest since the delisting of XMR, ZEC and DASH I don't expect much more from Bittrex. Btw I also still have Dash on there and they take 0.05 Dash for a withdrawal(only HitBTC takes more). Just for comparison Binance(and many others) take 0.002 Dash.