I love "Posh Spice." I'm going to call her this from now on.

"Even though Cas got angel-sigiled away, he did see Posh Spice for a moment and he's full-on angel again. He should be able to find Sam."
Castiel still can't fly, and the show has never clarified if Sam still has the sigils hiding him from angels branded onto his ribs, so I just assume they're still there. Castiel may not be able to find Sam unless Sam prays to him.