It sounds like the puppy is doing really well! However a 10 week old puppy should not be given so much freedom that he can go off and make mistakes in the house.
Each time he messes in the house, it's reinforced - just because it feels good!
When your mom can't watch him like a hawk, she should put him in a puppy pen or behind a gate, so he can't go off and mess in the house. It's better to prevent mistakes than try and fix them afterwards.