Hitting the corner of a cobblestone wall physically deletes the items

I'm using a Huawei Y6 and bought the game, I noticed in my mob farm that when an item carried by water hits the corner of a cobblestone wall with an air block below it, it deletes the item physically, by that what I mean is that it can still be seen by the player but it can't be picked up by the player or by a hopper and after a little while the item will disappear.