Where are my TF2 items???

Yesterday I traded and ended up with some TF2 keys. Today I was planning on using them in a trade, but when I checked my inventory, they weren't there.

After a few minutes of looking into the guy I traded with (who seems legit), I realized that ALL my TF2 items are gone now. I had 6 items I received after a few hours of playing that I had never used.

Am I the only one having this problem? Has my account been compromised? Help me out folks, please.