This appears to be a situation where people were deliberately deceived, so their cars would be towed. They should seek justice and compensation through the courts from those who deceived them. Property rights aren’t, and shouldn’t, be an issue.
If the property owner had the cars towed, but wasn’t involved in posting the signs, then he/she’s not at fault and of course shouldn’t pay. The persons who posted or assisted in the posting of signs are at fault.
What it appears to be and what one can prove it to be may be two different things. However, we do know that the parking lot had “No Parking” signs posted and that those who parked there ignored those signs.