There's a small chance you can get the screen shot if you use a tool that searches chip RAM. I forget the exact name of it, but there was a utility I used to use (GfxRipper?) that would let you visually scan chip RAM for graphics. It also had a mode where it would try to find images automatically.
You would have to get the highscore table up on the screen, then reboot, and start the program; of course you'd want to have the utility installed on a floppy that did nothing but start it up on boot, so that you overwrite as little of your chip RAM as possible.
Good luck!
*EDIT* I just Googled it, and the program is indeed GfxRipper. It has a utility to write the program to the bootblock of a disk, which would minimize the chance of overwriting chip mem while booting.
