Where are you?

Vanessa has been in a twin bed for about a year now and has never had any problems with falling out or being able to manage getting in and out by herself. Only one time have I found her asleep on the floor by her door (that she can open by herself), which I concluded that she must have been sleep-walking (since she hadn't cried at all) and decided that that spot on the carpet was a perfect spot to go back to sleep on. Well, the other night I woke up to "Mama...Mama...Mama". Usually, she will get up and come find me in bed without any problems. She wasn't crying, so I gave her a few minutes thinking that perhaps she was just dreaming. She kept calling my name. I went into her room and did not see her laying in her bed, yet continued to hear "Mama...Mama...Mama". I looked down and saw her laying next to her bed. Puzled, I wondered why she had not sat up, climbed back into bed or hadn't come into my room. Since her room is rather dark at night, it took me a second to realize where she was. UNDER THE BED! At least from her waist up, she was under her bed and apparently couldn't figure out where she was and, therefore, didn't know how to get herself out. I pulled her out and put her back into her bed, where she went right back to sleep. Since she had not been crying at all, I figured that she must have been sleep-walking again and feel asleep on the floor, then rolled or sooted herself into that position. She was not scared or upset, as I think she was still asleep through most of this and at some point woke up while under there and realized that it was darker than normal.