I submitted a bug report with the items I know are missing … still nothing on that front. I still do it though just so I can go back and tell them - maybe at some point they’ll figure out the warbank is not quite battle-ready and reimburse the losses. 
UPDATE (8/10)
Hey Blizzard -
Your war bank is still broken. I am now missing multiple items again. I have been using it sparingly now and from this point forward I’ll setup a new bank alt and just use my previous method of caching items. I keep screenshots so I know what goes away but even so… slots have just gone blank and I have not been sorting my bank. This “feature” is TERRIBLE.
The war bank SUCKS. I’m VERY frustrated that items are going missing and you have no recourse for resolution.
Items missing this last round:
180 x Tidespray Linen
262 x Shal’Dorei Silk
8 x Sumptuous Fur