Are you absolutely positive it stayed in your inventory? Hmm, maybe they patched it some time. Actually, I'm pretty sure the last time I had a completely wrecked weapon was the first time I played the game, which was on release day. I guess that kind of puts me out of touch.
Broken weapons stay in your inventory, they just automatically unequip themselves and can't be re-equipped until repaired. Had it happen with a combat shotgun last week. It has been that way for as long as I can remember, and I've been playing since day one. Are you sure you just didn't overlook the weapon in your inventory when it broke?
I too would like a "breaking animation" for each weapon, but something simple and just as realistic would be to keep the weapon equipped and just have it keep making clicking noises when you pull the trigger, regardless of available ammo. Every couple of times you pulled the trigger after that the game could just show the message, "This weapon has broken. You must repair it to use it again."