Whenever an item is picked up by a player in the latest snapshot, the dropped item entity disappears as it is moving, however the shadow still remains. This is not the case in 1.15.2, where the item pickup animation is normal.

Some things to note: this is a visual glitch, not functional. The item still appears in the player's inventory. However, it can be disorienting at times and confuses the player about if they picked up the item or not, and they always have to double check if they did. Certainly a very minor glitch, but slightly annoying.