Oh my! Ya know you are not the only one it has happened to! When we were still in Alaska I took Teddy and Chloe (our golden) out somewhere. Chloe had been laying quietly in the back and hadn't even popped her head up so when we got home...I forgot she was even in there! I grabbed Teddy and went in the house. I think it was about 2 hours later when my son said where is Chloe!
It was cold out, thank God...she loves the cold weather. It could nave been disastrous if it had been hot out! I won't even take her in the car if it is warm out at all. Poor thing was laying there in the back seat looking like I had interupted her nap when I raced out to get her.