I feel your pain ... I'm doing a bargello right now - a "mirror" image and I sewed the right side just like the left! LOL Now I have to take it all apart! At least mine's not quilted.
OK - for your's ... honestly, it took me about 5 minutes to find your mistake!!!!!! And I was LOOKING for it since you mentioned it ...
It's a gorgeous quilt, and the only thing I would do is what maniacquilter suggested.
Good luck!