I picked up two protector containers earlier this week from NWAF Firestation.
They were placed in in the bottom of my bag, with my medkit and ammo box in the slots above (35 slot bag).
The next day, I noticed that the bottom section of my bag had been rearranged and I was missing a case. I was confused, but didn't think too much of it.
Yesterday I logged in and the second case was missing now. Between these times I had swapped to a 30 slot bag.
I haven't been able to reproduce as I haven't found any more protector cases but will when I can.