Towing Issues: Wrongful Tow?, physical proof, tow company

Question
Is there any way to get the money back after your car gets towed?  I met two of my friends in a parking lot that was shared by many businesses and went into one of the
restaurants to eat brunch, then walked off the premises only to return approximately 4.5 hours after leaving the restaurant to find all three of our cars gone.  We just stood there stunned until someone yelled across the parking lot asking if our cars were missing because hers was as well. We went inside a restaurant and they said they didn't have them towed but gave us the number to the tow company. They confirmed they had our cars so we found a ride to the tow company (about 7 miles away) to find out that we each needed $150 cash to get our cars.  None of us saw any signs in the lot saying we couldn't park there.  I later went back and did find the signs, however they were not in a place I would see unless I was intentionally looking for them (they weren't facing in a direction for me to see when I was driving).  Also two of the three of our reciepts say the call time for our car being towed were while we were still in the restaurant eating, the other was 40 minutes after we left the restaurant.  We had paid in cash at the restaurant (not knowing we would need it later) so we don't have our recipt from the restaurant.  Is this allowed?

Answer
There is still more information that is needed to properly answer your question but most inner city parking lots have designated parking spaces for each business. Since I don't know exactly the situation I would assume the vehicles were parked in the wrong spots and or for too long. Also your case for a refund would be difficult since there is no physical proof (receipts) as to to your whereabouts and time limits.