Am I a terrible mom?

My son rolled off of our bed. We have it up on 5 inch risers. On the way to the floor I heard a smack on his crib. 😢😨 and I don't put him on the floor very often, because it's so filthy. (We live with my family, and they've got 2 big dogs and their carpet is beyond stained and in some places is falling apart) We vacuum about once a week, and keep the dogs upstairs or outside as best we can. 
I'm sure he's not the first kid to roll off mom and dad's bed. (I was making a bottle and listening to him from 15 feet away) but I feel bad.