Contest the ticket. Check the contested box and mail it in. It doesn't hurt to do this, and gives you time to see what evidence they have.

Once you get your court date notice back, make a Request for Discovery and get the officer's notes and all proof of the infraction. Make sure that request is certified mail or some other traceable method. Look online for the language to use.

If you get the requested materials, review the evidence. Since it sounds like the officer lost sight of you, they will need some proof that they measured your speed and tag number (e.g. laser photo) so they knew they were pulling over the right car and not something similar. If there's no proof that it was your car, or if you don't receive the materials by the court date, go to court and request a dismissal.

Since the ticket was issued quickly, there's a chance you were measured by another officer. They sometimes work in teams on I5 with one officer on an on -ramp/overpass or airplace, and a group just chasing down drivers handing out tickets. These usually can be thrown out as heresay unless the ticket is issued (along with notes) from the measuring officer.

Even if they have proof, since you claim you weren't speeding, testify as such. Bring any evidence you have. Dashcam, passengers, etc. If this is your first offence, I've seen judges accept a defendant's testimony and lower the fine or dismiss. This is a last ditch effort, and low chance of success, but I have seen people admit to speeding but "had a screaming kid in the back", or "really had to pee", get let off. Really depends on the judge.