It is not uncommon for a customer to come to us with the remnants of a design, asking us if there is anything to salvage. The good news is that we do so regularly. The time and effort 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 obsolescence, restoring the source files so the board can be modified for additional functionality, or presenting it 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.