It is not uncommon for a customer to come to us with the remnants of a design, asking us is there anything to salvage. The good news is that we do so on a regular basis. The time and effort it will take will depend on what file(s) are available and what actual hardware can be referenced.
Restoration is a broad concept. This can be anything from updating a board due to component obsolesce, to restoring the source files so that the board can be modified for additional functionality or presented to other fabricators and assemblers for manufacturing.
We could spell out all of the different files and scenarios, and we have. For those who want to take charge of a PCB translation project themselves, we've put together a "Translation Checklist" guide.