Items in inventory and frames going missing.

What I expected to happen was...:
I expect items I posses to remain where they were placed

What actually happened was...:
Twice now I have logged in to find items missing. First I had a diamond pickaxe placed in a frame that disappeared. The next time it happened I logged in and a map I had in my inventory was gone.

Steps to Reproduce:
I don't know how to trigger the bug. the only thing that I do is log in an I notice that things are gone.