I did not see a picture - but I think I would fix it by hand.

You realy don't think this quilt is unacceptable as a gift now, do you? If you don't mention it or draw attention to it no one wil notice and it they do, they really won't care. They will have received a beautiful quilt from you. That is way more important than two mis placed triangles. Perspective! IMHO
peace

I wouldn't touch it either. It doesn't sound like a blatant mistake. A non-quilter will most likely never notice, but remember something else. The Amish purposely put an error in every quilt because they believe no one is perfect but God. :) :) Something to ponder, huh? I personally think the mistakes are a lovely reminder of the person who made it.

I'm fascinated by how the replies in this thread split between "don't bother - no-one will notice, the quilt will still be loved, and no-one's perfect" and "do something about it because it'll drive you crazy if you don't fix it". Really reflects how different we all are in our ability to tolerate errors! I've moved from one to the other - when I started quilting I picked up that I was supposed to aim for perfection, and it often made me very miserable. Since then I've relaxed a lot more, and as long as I know that I've done my best, I can forgive myself my mistakes, and take the view that I learn from them.
But it would be a dull world if we were all the same!