I normally do not wash a flimsy quilt, at least in a washer. BUT I have soaked them in a bathtub depending on how bad they might smell.. Yep, I've been given really stinky flimsy's that stunk so bad I had to do something before I could continue.

Oh, you poor thing! I, too, have done an "oopsie", so I can sympathize. Please let us see the finished product. Good luck and lots of patience.