Leaking fluid from in front of my driver's side rear tire

It's not gasoline as my tank is on the opposite side. But when my car has been parked for a few hours, I can see a small puddle left there but I cannot see anywhere that is actively leaking. When I look underneath my car nothing looks wet on my car itself. However, my car was pushed backwards about a foot to a foot and a half while parked by a pickup truck but there was no noticeable damage at the time.