|Ya I've lost track of where the Colt is too. I think the last time they used it or we've seen it, it was when they used it on Lucifer. |
I don't know if they could ever really have proof if the Colt will work on certain thing's(not counting normal things they have faced before). Cas and Crowley thought the Colt would work on Lucifer and we know how that worked out.
I could see them (and hey Cas too for that matter) saving it for cases where there's no clear other options and in the case of Faith Cas and Balthazar apprently had another option so they went with the sure thing rather than the one that COULD go either way.