I am sorry that happened, and yes it has happened to me. If the problems were mine (I didn't read flannel, thought it was cotton) and I could use it I just ate it. If the color wasn't what I thought, I returned it. fabric.com is great for returns. But if it isn't worth the postage I just use it in something. There are always grocery bags to be made! LOL!
Don't let it stop you from online buying though. There are some great fabrics out there just waiting to be adopted!