Nope, they're just ultra rare.
Rarebit posted the odds a long time ago on the loot drops.
Droprate is 1:24.
24 hours or 24 days?
All drop rates seem to be getting smaller for me, even the Smith Frags seemed to be taking a while to drop, I have went 3 waves without one dropping. I spent a while farming in Sakura too and only got 1 Mask to show for it (was a while ago so cant quiet remember the time I spent in there)
The odds on that are around we'll say 1 drop per 40-50kills, that doesnt mean in 50 kills you will get a drop. Its a really dodgy method of working out how many will drop per kill so... Even when you put that into perspecitve if its 1:50 in another 30 kills you should have three >.<
It works out at a 4% drop if its 1:25 so take that into consideration :/
The odds on that are around we'll say 1 drop per 40-50kills, that doesnt mean in 50 kills you will get a drop. Its a really dodgy method of working out how many will drop per kill so... Even when you put that into perspecitve if its 1:50 in another 30 kills you should have three >.<It works out at a 4% drop if its 1:25 so take that into consideration :/
*edit* double post
*walks away mumbling about crap-*CENSORED* forums*