I would take him back in and explain to the groomer about the short & long spots, and ask that she fix it at no additional charge. If you do not bring it to her attention, she will not know. I don't think it is intentional that they do a "bad" job so that you will take your business elsewhere. It takes a few times for them to get it the way you want, just like a new hairdresser with your own hair.
