Placing an item frame on any block will cause it to disappear, item frame subtracted from your inventory. Tried placing on several block types and can not see the item frame. Does not appear to be invisible, attempting to break it will only cause damage to the block it was placed on. Also, item frames previously placed on blocks do not show or are missing. Does not appear to be somewhere else as another bug post suggested. Searching the area, I couldn't find it.