Write it down. Document it. Now.

Production mistakes happen. It's part of the business. Hopefully they get corrected and the print shop moves on. What's frustrating is when the same mistake happens again. One good way to avoid making the same mistake twice is to document it in a journal. Two of my old "print experience journals" filled with technical production notes, test results, samples, and odds and sods of print-related information.
A "print experience" journal can be used to document mistakes and how they were corrected, prepress/press tests and results, samples of interesting print effects, and technical bits and pieces of information. Some print shops create a database, hosted on a server, of this type of information that CSRs, sales people, estimators, and production people can both access and add to.

Documenting production experience in an accessible form, like a journal or database, helps the shop learn from its past and reduce the chance of making the same mistake twice. They can preserve the knowledge inside the company even when key employees leave the business.