My friend is dating my ex!?

Well, my best friend, Tasha is still great friends with my ex, Ty (who I still really like). So she posted an inside joke on facebook that said "H.A.P. lol Ty." Then my other friend, Katy, said "What?" on the post so then Tasha said "Oh, nothing." So then Katy said, "Well I'm dating him Tasha! So happy." I'm not sure if they were chatting and talking about a different guy or Ty. I'm so confused. I know Katy has liked Ty for a long time but he told me that he has never liked her! So, How should I ask my friend if they are dating? (If you misunderstand something she seriously SPAZZES OUT at you!)