I have had this happen, were loot disappears, however on occasion I have also seen it re appear about 30 seconds after, and sometimes a few meters in a random direction from where I was standing and placed in on the gound. Maybe a server lag issue?, this I'm not sure on.

I also can confirm this and have used all levels of quality of suppressor.
Test M4 items were
Pristine - Buttstock MP
Pristine - 30Rnd STANAG (coupled)
Pristine - ACOG optics test
Pristine - Green handguard MP
Worn - ATLAS bipod
Pristine - Suppressor 556
Same noise levels heard as no suppressor. Also tested ruined, badly damaged, damaged and worn variations as mentioned.

Also confirm, ammo disappears when you empty a clip "in the world"
Also if you place a "box" of round in an ammo storage box, and attempt to unload it the ammo disappears again.

*edit* I mean empty the rounds box not unload it

Can confirm also.