There is no reproduction. It's part of the UI.
Expected Results: Add a bit more space for the bags in the inventory system.Edit to original post. (read Trendy's reply. Thanks guys/gals)
When you go to the Filter Tab, the items in the missing bag are shown. So, it appears to be just a bug.
This was found after running a map, as I have the missing bag only set up for picking up pet food.
-regards
We have determined the cause of this issue. For the mean time you can access the items in your first bag by using the "all bags" tab.