I'd try calling again ... and again ... and again
I don't know if this would be feasible, but there is a 930am nonstop from CVG; return leaves LAX 1220pm ar 720pm (which isn't radically different than the 1145 CMH flight you currently have, but if your car would be in Cinci it wouldn't make sense to fly back to Columbus)
there's also an 815am over Detroit with a 2+hr layover, arriving LAX at 210pm