Why isnt Linda featured?

Maybe it's because she and Jeff Anderson (Randal) got divorced.. Could be that they had a bad breakup and she chose to also divorce herself from all things "Clerks." Of course, there could be no "Clerks" (or sequels) without Randal, but since Kaitlin cracked up in the first Clerks her character's sort of irrelevant now.

There's a "Snowball Effect" outtake (which can be found in the special features on disc three) where Kevin talks about seeing her in an acting class, and basically how he met her.

"Who knows where thoughts come from? They just appear!" - Lucas, Empire Records

She was living in Jersey, with a newborn kid... didn't have the time to travel out to Los Angeles, didn't have the time to do an interview the brief time that the documentary team was on the East Coast. She wished everyone well, though.