IMHO, the question would be if the clip occurred while the ball was alive. If B fielded the loose ball while on his knee, the ball would become dead upon his possession. If the clip occurred prior to that then 1st & 10 @ B's 3 would be correct. IF the clip occurred AFTER the ball became dead it would fall into the DBPF category with succeeding spot enforcement. If so, 1st & 10 @ B's 20. Remember, guys, the foul would have to be in the USC/DBPF family to be a foul...i.e...you can't have a dead ball hold or dead ball block in the back.
AND REMEMBER THE 4 W'S OF CALLING A FOUL......
WHO, WHAT, WHEN,