AFK bug or Alt+tab glitch

While i was afk in a box fully surrounded by blocks so nothing could get in i somehow died. i thought maybe a creeper had blown up all of my items or something but that was not the case. when i re spawned i had all my items and the box i was in wasn't even opened and it seemed like i had died to hunger or something but as the video shows i died to a zombie villager 

https://www.youtube.com/watch?v=cMoOltiqlOs&feature=youtu.be

sorry its a youtube link but the file is too big to attach