Yes, you were together fighting Billie, and then you were gone. He was upset so he didn't go into detail.

[ For the obvious reason, and also because Dean is Dean. He wouldn't say more toward Jack even if he felt like explaining. Jack straightens out the aisle and returns Castiel's very direct gaze with his own. This isn't unusual for either of them and he assumes they're on the same page. ]

I missed you. I was worried the world would end before I got to see you again.

[ It probably should not have been high on the list of concerns when they were fighting God, but Jack is a simple enough youth. He cares about his family above most things. ]

It's okay though, we had a plan.