My armour disappeared on my armour stand.

Put the summary of the bug you're having here

*What I expected to happen was...The armour would stay on the armour stand.

*What actually happened was..My helmet disappeared first after a week, then the rest after a month of not entering the game.
Describe what happened here

Steps to Reproduce:
1. I had full enchanted lv 30 armour and put it on a stand. I was in survival mode, no cheats, and singleplayer.
2. ...It was looking at a window
3. ...not exactly sure what had happened to it, the armour stand was there, not the armour