ok, in LLS(9) MCL, Larry Lovage has LLS4 The Missing Floppies on his deskstop computer (with a 5 1/4 floppy drive BTW). There is only one scene, and it shows Larry Laffer in front of a brick wall of some sort.
But there is another mention of LLS4 somewhere else. In Space Quest 4 The Time Rippers, we can read a story of the fate of the planet Xenon. Sometime after 2735, it says that they found a box floating in space with the words of no other than “Leisure Suit Larry” on it. The guys loaded the disks onto the planets mainframe which also controled the planet’s weather and factories, and a virus took over. A deep voice (Sludge Vohaul’s voice from SQ2) said “Wilco must DIE” and Vohaul took over the planet. Later in the SQ6 when Wilco dumps the infected file out of the mainframe, the file “LLS4” is the infected file. So LLS4 was the game box floating in space.
So….. the content of LLS4 is still a mystery, but how Sierra lost the game before it was published is solved….