No Overnight Parking

We stayed at this Walmart about a month ago for a night. Didn't notice any signs and there were several trucks parked. We tried to stay another night now (a month later-i had a Dr appt in the area) and the manager knocked on our door and asked us to leave. Said there were signs and NO ONE can stay overnight. Sure enough there are now signs "No Truck Parking". He was quite rude about it. We were very courteous and left immediately.