Hi J.,
I wouldn't worry. I know that this isn't exactly your issue, but... Personally, I was fearful when our daughter was going to transition to a "big girl" bed. She was just so active in her crib that I feared the railings wouldn't keep her from falling off in the areas that they didn't cover. So, our solution was to put her in an air mattress. She had regular sheets and pillows and all of her crib comforts. The best part for me was that I knew she wouldn't fall out in the middle of the night--or if she did, the floor was right there. There were many times that we checked on her and she was half off the bed on the floor; but she was comfortable. Then, as she grew out of that, we started encouraging her to think about moving into the "big girl" bed. She did when she was ready. Yes, she was able to get out and explore, and times when she would fall asleep on the floor somewhere--sometimes it still happens, but rarely--I think that your daughter is exploring her new-found space. Once she gets used to having the access to all of her room, you'll see her stay in her bed.