Diagnostic but failed to service

I was really hoping to find a great honest mechanic in the area and thought Mastertech would be that place. But we took our Mini Cooper in to get an inspection done and for some reason, on that day, the service engine light was on. Therefore, they couldn't inspect it. We paid for a diagnostic test to be done so we could get the work required done to pass inspection. We were told that the part would need to be ordered and it would take about 2 days to come in and it would take 1/2-1 hour for the service. I was quoted a price over the phone for the repair. He told me that Mini did not carry the small part that was needed and that he was going to have to get it from another auto parts store and go pick it up. He said that Mini only sells the entire assembly which would be much more expensive. But over a week went by without a phone call to tell us the part had arrived. So we called on a Wednesday and they said they would call back. Never did. We called the following Friday and they said they would call back. Never did. So we called the following day, Saturday, and we were told that the tech guy who quoted me the service was now in the hospital and that they couldn't do the repair because they don't know the exact part to get. They referred me to Mini and to get a rental from them, which is now going to cost me major $$. Remember...the tech guy told me that Mini does not sell just the small part needed (only the entire assembly). Not to mention that Mini (the dealer) charges 300% on their parts and labor. Chris, the one I spoke to on Friday and Saturday, seemed to not know anything. He just told me to take it to the dealer. If I would've known they wouldn't do the repair, I would've had the diagnostic test done elsewhere (somewhere that could). Because now, I am out that diagnostic fee and it cannot be applied to my repair as they promised. I feel terrible that the tech guy is in the hospital, but it shouldn't be that difficult to know which "pigtail" to use in our car when they have all my auto information on file (make, model, VIN, etc.). VERY UPSET AND DISAPPOINTED!!