Bless your heart.
I'm so sorry this happened. But I understand it. We get too close to what we're making, I think and sometimes just can't "see".
Who says the back has to be like the pages of a book? Instead of a turn, you'll have a flip. I think it won't matter....and in fact, can be interesting.
I sewed a back on crooked once, and it was a print that showed it was crooked, too. I didn't discover it until it was quilted and no way was I ripping it out. It taught me something, though, to check and recheck the backing, especially if directional or a print with lines. So, I suppose no experience, no matter how bitter, is meaningless.....if that's not too Pollyannaish.