The apps that transfer items, such as the Companion App and Destiny Item Manager, cannot delete, dismantle, or remove items entirely from existence. The only way for items to go poof are from manually doing so yourself within the game or through an update by Bungie that removes the item from the game. Transferring an item from one Character to another moves the item through the Vault. If the Vault is full, or the intended Character is full, then the item is left in its previous location as part of the move. If moving from CharA to CharB, it moves from CharA, to the vault, to CharB. If CharB is full and cannot receive the item, the item remains in the Vault. If the Vault is full and cannot receive the item, the item remains on CharA. The apps, however, aren't always prepared for this situation and don't always update their inventory list to show where the item has gone. You'll need to refresh the app so that it re-gets the inventory, or check in the actual game. Your item does exist, either in its original location, the vault, or its intended location. There are no other options, as, again, the apps cannot make items go poof.