Propbably the best way to find out is just ask the seller. Hope this helps.
You have recieved good answers.
To elaborate on if it was a foreclosed home, I have seen the previous owners take some silly things from the home before. The last one I saw the previous owners took outlet covers, all lighting fixtures, toilet seats, the doorbell outside the house, etc.
To add to Bryant's comment, it was most likely done for painting purposes. When the owners strip the home, their target is items of value ie. washer, dryer, refrig, AC unit, etc. If they were angry, and in a destructive way ,rather than removing outlet covers they would be breaking things....which does happen.
The "Eckler Team"