The default UI is showing 2 shared bank slots. Custom UI: AngUI shows 4 shared bank slots. http://postimg.org/image/6y1hezgax/ In the screenshot the fire beetle eyes and carapace were gone upon relogging (also lost one of my ragefire bags that way). In general: If you place items in the bottom 2 slots that the AngUI shows then relog those items will disappear. The items in the top 2 slots are fine.
Additional testing: Closing the bank window and reopening it did NOT delete the items. Zoning caused the items to be deleted.
My guess would be this is exactly right. However the UI shouldn't load in order to prevent an issue with items disappearing.
Problem is that custom UIs are not supported by DB. That is an issue with the UI itself and needs to be brought to the creator. Disable the custom UI and test the slots without it. If there is a problem then, then it becomes an issue
This is all well and good but what of the lost items. I had been seeing the "slots" but didnt use them till now. How do we get the items back??
There are only 2 shared bank slots available on Ragefire. If you somehow saw the other 2, which are on the regular live servers, and used them, you risk losing your stuff. That's a bug with the UI allowing you to see them, not the game.
You can try to /petition, but I'm not sure how much luck you will have. GM staff is seriously under resourced, and many of these kinds of issues were met with the response, you need to reacquire the items in game.
I would posit that the other 2 shared bank slots you saw were actually your "shroud" bank slots. Shrouding is a Depths of Darkhollow feature where you can morph into a creature and play as it, and those slots are reserved for them exclusively.