See James Bond Music page on Facebook on 2nd April 2021 :-
The Moonraker myth started when the expanded CDs came out in 2003 and Lukas addressed the question of why Moonraker wasn't included.
Basically tapes for Moonraker were not stored with the other tapes they were working with and there was no budget to go looking. Besides, the 5 scores to be expanded had already been determined.
It got misquoted into the Moonraker tapes being lost and that became urban myth.
People even started saying the tapes had been dumped by Davout, the Paris studio where Moonraker was recorded.
However, these myths were based on a number of false presuppositions.
First, for a major movie like Moonraker there is never just one set of tapes. There's just too much riding on it. It's very likely that both a master and backup copy were taken at the recording session, and then there may be other duplicates created for other purposes.
Second, in order to get music into a film's soundtrack, you have to do more than just record it. You have to dub it. The dubbing happened in England. Jon's book The Music of James Bond confirms tapes were shipped to England for this purpose. There would have been no reason to send them back to Paris, since Davout is a recording facility, not a storage facility.
Now, of course none of this proves the opposite, that there are accessible tapes, but several people who would know have assured us there are Moonraker tapes and they have been preserved digitally.
So, basically, a misquotation plus some false assumptions and Chinese whispers equals urban myth.