Sleep walking?

Since we've moved into this new house and no longer have stairs to worry about Chris told Alex that when he wakes up in the morning or from naps he can just come out of his room and find us. This has worked out pretty well since we have the only monitor in Zachary's room. The first few days if I heard him and opened his door he would tell me to close the door so he could come find me. Very funny. This morning as Chris was leaving for work around 7 am he noticed Alex's door was open and he wasn't in bed. He looked around the house and found Alex asleep on the couch in the living room. Chris just picked him up and put him back in bed. This is the first time he's ever gotten out of bed during the night. I wonder why he didn't come to our room? To my surprise both boys are still sleeping at 7:55 am.