I was standing next to a rock and had to place an item in the vicinity box in order to rearrange my backpack inventory. When I went to pick it back up a few moments later it was gone. I then realized that I was standing next to a large rock and the object must have been placed on the ground plane but under the rock. I then tried reacquiring the item from several different angles and positions around the rock with no success.
{F32239}