Yup, it happens, it happens much too often.
I was quilting a shop owners block of the month display quilt and found one row of blocks she put upside down. Too late, I had already quilted most of it. That she was able to applique that row over the row already in there. But you don't have that option.
You know they are going to love and appreciate it no matter what. They are going to appreciate the love and work and time that went into it. Then of course you will get teased.