Detective Kusto: 'Til the End of Time

The year is 1992, a chilly night is falling over the city of LA. You are naping in your office listening to the radio and smoking your pipe here and there.
A shadow of a figure shows over your blured glass of the door, the person slides a paper below the door and runs away.
Strange situation indeed. You pick the peace of paper up and read:

"""
I have been watching you, Detective Kusto.
The best detective in LA, they say.
I say let's put that to the test.

Someone you once knew is gone. Not dead — not yet — just... relocated.
The world hasn't noticed.
The papers won't write about it.
His boss thinks he quit.
His neighbors think he moved.
But you'll notice.

Because I'm telling you to.

Go back to where it all started, Detective. Jefferson High, class of '74.
That's where your investigation begins.
"""

Not a popular case, no money, no publications or popularity. Will you accept this case?