Whats up with the weapons disappearing?

So how often has this happened to you, you’re playing campaign or spartan Ops, and you kill an enemy that has a weapon you want, so you kill it, only by the time the you get to the corpse the weapon is gone, nowhere to be seen. or say you’re playing co-op campaign or spartan ops and you die, and by the time you get back to your body, again the weapons have disappeared.

That is not a hugely game-breaking flaw, but I feel it should be fixed in a TU epically for those who’re trying to make a Legendary campaign/spartan ops run. it sucks having to go to the trouble of prying a power weapon from an enemies cold dead hand(s) only to have it pulled out from under you.

However I can’t say I’ve had this happen in War games though, unless some one cares to share on that.

Also is it just me or do too many grunts/elites in spartan ops chapters have FRGs?