HELP! Was it my fault?

Okay, so last night my uncle left his laptop on the floor and then I used it and put it back there. When I used it, it was in perfect condition. When I left it, it was in perfect condition too. So this morning when I opened it, it had a scratch on it. My grandfather who was sleeping on the bed when it was on the floor he probably got a scratch on it. Now my aunt and uncle are yelling at me and I'm saying it's not my fault. Well is it? Or is it not?