If a player's ball is stopped or deflected by his own or his partner's equipment, he incurs a one-stroke penalty and must play the ball as it lies.
When Player A’s putt strikes Player B’s ball that has been marked, lifted, and set aside, Player A’s ball has hit Player B’s equipment. Player A must play his ball as it lies [Decision 19-5/1]. There is no penalty to anyone.
You have to ask yourself why Player B didn’t put the ball in his pocket after he marked and lifted it. His carelessness affected someone else’s play and was the catalyst for two weeks of argument.