Somethings I do whenever I send a knife back for a tune up or warranty repair. I never assume "they know":
1. Put a strip of blue painters tape with my RMA# across the cutting edge of the blade. If no RMA is given, then i write my name on the tape.
2. I also put a string tied price tag type thing through the lanyard hole with the RMA# or my name.
3. I've used adhesive address labels as well on the blade so they know who's knife it is.
4. Include a typewritten letter with all your contact information at the very top, including a phone number. Explain in detail what you want done and not done to the knife. Describe the problems, and how they can replicate them if any. Provide instructions to contact you via phone or email if any problems cannot easily be repaired, or if the best option is replacement.
Again, the trick is never to assume that any manufacturer will know what is wrong or who belongs to that knife. Make it easy for them to identify and fix your knife, it may mean a faster turn around time and a better job in the end.