The only time I have seen an FQ without one selvedge is when I bought some hand dyed fabric at a quilt show. The sizes were way wacky because they were cut out of wider material.
I did one quilt which was a pattern for fat quarters, and I had to supplement also, mainly because I worried about getting straight grain without worrying about how much I cut off the edges to get it!
I learned my lesson and my next quilt - a 'scrappy' medallion - I bought LOTS of them and made sure to lay out every one, press it and measure it against my cutting board to see if I was going to come up short.