20-1. Lifting And Marking
A ball to be lifted under the Rules may be lifted by the player, his partner or another person authorized by the player. In any such case, the player is responsible for any breach of the Rules.
The position of the ball must be marked before it is lifted under a Rule that requires it to be replaced. If it is not marked, the player incurs a penalty of one stroke and the ball must be replaced. If it is not replaced, the player incurs the general penalty for breach of this Rule but there is no additional penalty under Rule 20-1.
If a ball or ball-marker is accidentally moved in the process of lifting the ball under a Rule or marking its position, the ball or ball-marker must be replaced. There is no penalty, provided the movement of the ball or ball-marker is directly attributable to the specific act of marking the position of or lifting the ball. Otherwise, the player incurs a penalty of one stroke under this Rule or Rule 18-2a.
Exception: If a player incurs a penalty for failing to act in accordance with Rule5-3 or 12-2, there is no additional penalty under Rule 20-1.
Note: The position of a ball to be lifted should be marked by placing a ball-marker, a small coin or other similar object immediately behind the ball. If the ball-marker interferes with the play, stance or stroke of another player, it should be placed one or more clubhead-lengths to one side.
Refer to the highlighted last sentence of the "Note:" in Section of 20-1 of the USGA rules and decisions.
I'm not a rules guy so I don't know if the "Note" section carries any weight?
I'll let the more knowledgeable members answer that.
At a minimum I would say that Player B violated the sporting spirit of the game.