If a can of peaches is stored in a cooking pot placed on the ground, while my remaining inventory is full, the acto of opening the peaches will cause them to disappear. More simply, if my inventory is full, and I come upon a can of tuna, opening it while double carrying a weapon will cause it to disappear. Most common with canned food, but sawing a shotgun will also make it disappear, rather than fall on the ground.