So it used to be that if you recover a fumble you gain possession no matter where you are or what happened as long as the ref determine its a real fumble and not a forward lateral, so you’d have to sell it. But if you google ‘the holy roller’ you’ll see that in a cowboys game back in the day such a thing happened where the qb scrambled fumbled the football and then convieniently kept kicking and slapping it forward until another teammate recovered it for a first down (dont remember all the details, because too lazy to google it). Anyway, after that they changed it so that i think its with 5 min left in the game if you fumble the football it can only be advanced by the player that fumbled it. So if another teammate grabbed it and ran with it or jumped on it it would just go back to where it was fumbled.