I took my car to meineke to get some work done. They put on a part wrong and broke it and caused an…

I took my car to meineke to get some work done. They put on a part wrong and broke it and caused an oil leak. They noticed it when they took it for a test drive. The part they need is on back order. I have their loaner car which I got before they broke mine. The man seemed nervous at first when he called like he was expecting me to mad. I’m just kinda disappointed and want my car back. Would it be unreasonable to ask them for like a 10-20 percent discount when I eventually get my car back? He said it may be a while but he was going to call around and see if they could find it somewhere else. I know I won’t get it back until at least next week.