Mechanic left the brake cap off reservoir 6 weeks ago

[Benzasaurus]

I was showing my cars for sale yesterday and when we popped the hood on the sedan I immediately noticed that the cap on the brake reservoir was missing. I'm going back Monday morning and I'm going to give them hell.

But the receipt is from 6 weeks ago. What really pisses me off is the possibility they found cap lying around the shop and didn't call.

So how screwed is my brake system? Do I need them to be replacing the lot because of internal rot at this point? I have no idea how to convince them to do that given the date on the work. And now I feel nervous having them do the work itself!

The irony is that I took it in to them because I like a professional to take care of safety issues. This was the first time I took my car to someone in New Jersey after moving last summer. Jesus Christ.

And some forum members may have read my other thread about moving to Switzerland. I'm supposed to move in 2 weeks! Today a friend agreed to babysit it for me if it didn't sell. He has three children and was looking forward to Sunday driving it. The thought of them in it without any brakes...