Michael J. Fox's iconic Back to the Future guitar is missing

In an extract from his new memoir Future Boy: Back to the Future and My Journey Through the Space-Time Continuum shared by Us Weekly magazine, Michael wrote: "In the decades since the movie's release, the guitar used in Johnny B. Goode has grown more important for what it isn't than what it is. What it isn't is available.

"I wish I could claim to possess it, but I didn't have the foresight to know how valuable it would become.

"Somebody did, though, and whether it's in their active collection or stashed in their attic or home studio, they're not speaking up. Perhaps they're waiting for the statute of limitations on vintage guitar theft to expire."

Michael noted "collectible guitars are demanding exorbitant prices," and the price for the Gibson ES-345 - "is huge."

He revealed manufacturers Gibson have also "taken up the search" for the missing guitar and want to make a documentary about it.

He wrote: "Even going so far as to sponsor a documentary film chronicling the quest to find my famous red rock and roll machine.

"They haven't found it yet; the documentary's eventual release is linked to the existential discovery and retrieval. We'll keep you posted."

The actor admitted the scene, in which Marty is "giving the performance of his life" when he goes back in time to attend a 1955 school dance, was his "favourite" in the movie.

He wrote: "This is my favourite scene in the movie - obviously. It represents dreams coming to fruition; me doing for me what Marty did for himself.

"What was happening in my life at that moment was no less transformative than what was happening in Marty's...

"He literally saves the world with his guitar."

And while he "worked harder" on that scene than any other in the movie, Michael admitted it wasn't "truly necessary" for the story but was included "for pure joy".

He wrote: "The dilemma for the filmmakers is that the 'Johnny B. Goode' scene isn't truly necessary. Not only does Marty's performance fail to progress the plot, it arguably interrupts the plot...

"The scene adds a time travel joke, shocking the 1950s teenagers with the kind of music their kids will someday adore. It also releases the pressure from the preceding scenes.

"Tensions resolved; now let's have some fun."