Evie, that is really bad! It looks like you lost about 12 inches of usable fabric.
As a side note, I got back my quilt from the long armer, with regards to this question. Since I had to take a second backing (minky was not wide enough), I had to prepare a second backing while the top was at the long armers.
I asked her not to trim the quilt, so I could see if the backing was completely square after long arming, (since i had ripped it and used selvage for perpendicular side). To my surprise, the backing was completely square!
So this time, and for this fabric, ripping worked for squaring. I have to admit, I'm shocked.....