Personal item placed in my spot

I recently boarded a flight and attempted to stow my personal item (backpack with laptop) under the seat in front of me. It was unable to fit so I stuck my feet under there and discovered another backpack. The person in front of me had placed it there so he could stretch out his legs. It was a short flight and wasn’t worth calling a FA. The seat next to me was empty, so I slid his bag waaay over to make room for my feet and my item. After landing, I enjoyed watching him contort himself to reach his bag.