OK thanks...
I've poked around in the database and the code a bit. I'd like to have something definite to tell you here, but due to a (possibly necessary) quirk in the logging of stacked items going in and out of storage, it's unfortunately not possible for me to completely track the way bottles of milk were moved in and out of the bank chest. The counts of bottles going in is accurate, but pulling them out only reports a "stack" of indeterminate size. If I could make some determination there, I could potentially then prove possession if there was a disparity between the net deposit/withdrawal and what the bank currently says you have (which is 15 bottles), and you could get the balance returned to you. That is presently not tha case.
I have not tested anything directly, but I do wonder about some oddness related to stack sizes. It might be worthwhile to put only full stacks into a chest (of any sort) or at least not allowing the chest to do the stacking, meaning if there is a stack of three bottles and you add eight bottles. Do stacking in your own inventory and put whole stacks in before partial ones.
I'm going to move this over to bugs so it may get some attention and testing.
