What happened to the .50 caliber? That is a game-changing weapon, securing it should have been a high priority for Rick and co.
Was that the gun on the back of one of the Woodbury trucks? If so, it was still at the prison at the end of the episode. The truck drove over a spike strip during the attack, forcing them to leave it behind.
I was unsure/curious enough to search something out about this and, if you can believe it, found a site devoted to vehicles of The Walking Dead
The Humvee was carrying the .50 and you are right, it stuck on the spikes. Also according to them it "jammed" during the assault, but I don't remember that happening. (thank god for ODV) Anyway, HUGH asset for them if they can get it functioning again.