this sounds like a bug?
and this is where to post them
or was your inventory full at the time?
EDIT
if it was full they CAN de spawn so if you didn’t notice then… (and i also notice that sometimes certain items seem invisible (only noticed when dumping them or throwing my inventory at someone (trust me, do not trade that way anymore lol) - a few times i have been like did you get it? nope a few secs later… oh i just picked them up (the pick up message appears but neither of us could see the item once it dropped)