Already got my power armor and did some repair and upgrades, parked it at the red rocket, did some building in sanctuary and came back an hour later. It's now missing. Not there. Cant figure out something or is it a bug?

maybe it's like a horse and it returns to stable.

Some homies took it to a chop shop.

Was it insured?

Did you take the Fusion Core out before you left it? If not...someone may have taken it for a spin.... NPCs are MUCH smarter this time around.