Gym decay

I know this is a stupid question, but do pokemon return after their motivation gets too low, regardless of being attacked? I wouldn't normally ask, but i did some travelling this season, and dropped a mon off in a small town (approximately 100 people) in a gym that had yet to be claimed yet. I'd thought I'd found a gym that would last for months, but 3 days later it was kicked out. Even then that could just be bad luck. However, at our destination there is a gym near the house, and both me and my wife dropped a mon in about 3 days ago. We both just got them back, but the rest of the mons who were dropped in anywhere from 2.5 days ago to 6 hours ago are still in, with no attack animation. Maybe it's just bad luck and odd behavior combined with coincidence, but both returned after approximately 3 days, when both seem unlikely that they were attacked.