I too can't find the mistake on some of the quilts when mentioned. I find on my own quilts if I take a photo of it, the error becomes clear as day to me but couldn't see it when it was hanging up on the design wall. Don't know why that is but these days I'll take a photo just so I know ahead of time before I go to quilt it Also it seems to help me see if the arrangement works. As to whether you should tell the person about the mistake, boy that's a tough one. Some don't want to know, others don't care to know. For myself, please email me privately and let me know....though if its already quilted, its too late as I know I won't tear it apart and fix it then..........unless its a HUGE, BLATANT MISTAKE. Then yes, I'll fix it.