Armor stand with armor on it relocated itself?!

I was digging in caves about 50 blocks down from my base. My armor stand is normally 2 blocks away from my bed and I never move it. When I came back up the armor stand was now 2 blocks away from it's initial position standing on my bed. It's a solo game. I did not move it and no one else could have moved it. Is that just part of the game?