WHY DID SCOTTY IN "RELICS" (TNG) ASSUME THAT KIRK HAD BROUGHT THE ENTERPRISE TO RESCUE HIM, AND HE KNEW PERFECTLY WELL THAT KIRK WAS PRESUMED DEAD AFTER THE ENTERPRISE-B STRUCK THE NEXUS IN "GENERATIONS"?
The Canon Answer:
Not addressed in canon.
The Non-Canon Answer:
William Shatner's "Star Trek: The Return", page 62:
Riker remembered his conversations with the feisty old Scotsman[...]After Kirk's first recorded death, on the maiden flight of the Enterprise-B, Scott had led an intensive search of the sector in which that ship had been damaged by the mysterious energy ribbon known as the Nexus.
Decades later, when the chief engineer had been rescued from transporter storage and come aboard the Enterprise-D, he had explained the details of his search, how he had used experimental sensors sensitive enough to detect individual molecules, let alone the body of his captain.
...Scott had found the remains of other victims of the force of the Nexus[...] but he had not found all of the recorded El-Aurian dead. And, more importantly to him, he had been unable to find any trace whatsoever of a human body.
And, on page 63, Troi says this about his "mothballs" statement (when Spock points out that [in Shatner's first Trek novel "Ashes of Eden"] the Enterprise-A crashed on Chal).
"It was what he hoped, Ambassador. Not what he knew."
Thanks to William Castner and Jon Hendricks for their assistance!
The Fan Answer:
The most popular explanation is that Scotty was a wee bit disoriented when he was rematerialized, and made the remark in error.
The Lowdown:
Simple. "Generations" was written after "Relics."
Moreover, the lines in "Generations" given to Scotty and Chekov were originally meant for Spock and Bones. When Nimoy and Kelley declined to appear in "Generations" (the roles were just too small, they felt), Doohan and Koenig replaced them, and the writers either forgot about the line in "Relics" or disregarded it, knowing that we fans could come up with a reasonable explanation. Had Scotty not appeared in "Generations," the explanation would have been far simpler: Scotty's mishap on board the Jenolen could have happened before the Enterprise-B incident.