New rescue horse escaped overnight looking for company now paired with an old mare - Day 2

New rescue horse escaped overnight looking for company, rejected by herd - paired with an old mare.
Both the herds we own rejected him. He was having a similar problem with the lady who rescued him (he was there for two weeks before coming to us). My thinking is, he is frail and the horses often shoo sick or frail horses out of the herd. So he left overnight and was found trying to get into a neighbour's paddock where there is a horse and some sheep.