I work part time in LQS. I see it happen all of the time....customers come in and buy either exactly what the pattern they want to make calls for and then they make a mistake or they didn't have enough and they come in and it is gone.....we always tell them to try on-line.....if it is fairly new this works..if not they have to substitute.....hard thing. I will see a line of fabric that I like and I will decide to wait to buy it and the next time I come to work it will be gone....drives me crazy!
So actually if there is a peice that I LOVE...I will buy 5 yards....because I feel safe with5 yard cuts.....if worse comes to worse....I can always use it for a backing... usually make pretty big quilts. I have also been known to buy a whole bolt of fabric if I thought I would use t specifically for backing.