If they willingly let an engine go through their shop that wasn't right, then the customer has every right to complain, though preferably to IPS in person first to give them a chance to make things right if it was truly a mistake.
As a consumer, I would like to know about any and all issues that customers have at businesses that I may patronize. I would also like to see how the business responds to unsatisfied customers. It is not difficult to determine by reading both sides if I want to do business at that establishment or not. Case in point, read the thread about Rolla. It is obvious that Rolla operates in an unquestionable manner. Professionalism and tact are sometimes just as necessary as competence in your business. If you lack one, you must have the other to stay afloat.