I don’t think I will ever get over this scene. Dean was desperate to get out of there. So the “full proof” plan he comes up with is making Cas worry about him. He knew, that if Cas thought anything had happened to Dean, he’d come rushing in. And Dean used that against him. Bobby and Sam were in that house too, but Dean set up his plan around Cas.
Can you imagine how Cas felt when Dean not only used the sigils he learned from Cas against him but also used Cas’ feelings as a weapon against him?
I don’t have to. There’s a scene in an alleyway a little later that makes it pretty clear how Cas felt. Oh GOD THESE TWO!