It's not that big of a problem if your rules are set up correctly. If you use some BS default you may not get credit for an 'Offensive Fumble Return for TD'. Common sense says he should get credit.
It happened several times this year. Once for some Raven RB scrub, once for McCardell, once for K-Rob, probably a couple more in there as well. Your league really should have addressed this then
Some say there is a difference in scoring if the defensive unit recovers the ball, fumbles, then the offensive player recovers for a TD. Some think that would lead to a defensive TD. That argument is based on the concept of the D becoming the O, and the O being the D once a turnover is committed. If that were true, there would never, ever be a defensive TD scored. It would be impossible, by definition.
I guess that is what a commish is for. I'm not sure changing the scoring system to reflect a more common sense view is exactly the right thing to do. Once the scoring is set, I don't like changes. I do think that particular situation is an error and oversight on what MY league rules were intended to be, but I couldn't force that view on anyone else's league.
The meek ain't gonna inherit $#!%....'cuz I'll TAKE IT!