I'll be paying attention to this as well because Sammy is doing the same thing. She will be going to the vet as soon as hubby makes an appt for her. Same age, labx, doesn't know she's peed till after she's awake. She won't stay on a bed so she pees in different areas of the house.
I have limited her water intake at night but it doesn't always help. I think she gets into such a deep sleep (age related) that she doesn't know she's peeing.