i have to ask too....why did you wash it in hot water? did you have a (bleeder)? were you going for maximum shrinkage?
i purchase and pre-wash wide backings all the time- some shrink a bit more than others- but i don't wash anything in hot water unless i want it to shrink as much as i can possibly make it...
was it a loose weave?
i bet if you check their website and check the (care instructions) for that fabric line it probably tells you to wash in cold water or maybe warm water- i've never bought a quilting fabric that when checking the care instructions says to wash in hot water....