I'm weeks behind and just watched this episode, and I (unexpectedly) really liked it. But the thing that didn't make sense to ME is that Dean instantly fell for the ruse with the witch sisters, that he wasn't instantly suspicious, and the idea that he would not notice someone acting like an ordinary pickpocket at the very least. He's a man of the world and she was not subtle. Also, he has no particular medical expertise; why wouldn't he first pull out a cell phone and call 911?

I don't think he forgot about Becky; I think he was just dazed by the love spell. :-)