So I put some BTC on my account last night and I bought some TF2 keys. However, when I try to deposit/sell/do anything with them, they appear greyed out/unavailable and I'm absolutely baffled. There are no visible trades or orders that involve the aforementioned keys. Am I missing something? Thanks in advance.

If you see them grey and you do not have open orders for them it means they are being sent to you in a trade offer.