Blocks and item frames disappearing

In my singleplayer game I was away mining and when I got back to my base, there was a 1x1 hole in my roof and around 20 item frames had disappeared from my wall and on my chests. I at first thought this was a glitch so I tried to reconnect, but this didn't help.

After testing this, it looks like it was a creeper explosion, but what would make the creeper explode when I'm not there?