For the foul itself, it would just be holding. 9-3-7: "When the ball is loose, no player shall hold an opponent".
Enforcement can be a little more confusing if you don't break it down. The offense retains team possession while the ball is loose (2-4-1-c-3). Since it was a foul by the team not in possession, the 10 yard penalty will be from the basic spot (10-2-2-c-3). The action while the ball is loose is included in with the previous run as one running play for enforcement purposes (2-30-4-a&c). The spot of the fumble is the end of the run (2-25-8-b). If that run ends behind the neutral zone, the basic spot is the previous spot(10-2-2-d-1-a). If the end of the run is beyond the neutral zone, the basic spot is the end of the run which, again, is the spot of the fumble (10-2-2-d-1-b). When enforcing penalties for fouls that occur while the ball is loose, always remember that loose ball action is tied to the previous run, not any subsequent runs.
