old traffic ticket

What is the name of your state? NEW YORK
I received a notice to appear for a speeding ticket I don't remember getting from the year 2000. Isn't there a statute of limitations on these violations in NY?

Statute of Limitations refers to how long between the time you committed the crime, and how long you were charged with it. You were charged for the crime when the ticket was written, which was probably right after you were caught speeding, and I highly doubt the SoL for such a crime is less than 2 minutes. SoL does not apply to you.

Treat it as any other ticket. You would have to request discovery of the relevant records which include:
1) ticket itself (to check car description and other details)
2) radar calibration and test logs
3) officer's training record

Ask the court to postpone the hearing (aka continuance) until you get all records (can be as long as 40 days).

Bottom line, if you can prove you did not get the ticket, do so, but otherwise defend yourself with usual methods. Good luck.