Scene where Jen looks at the crystal's past

[Rob B]

I know that the part where Jen looks at the shard following his escape from the Garthim attack on Aughra's home that he witnesses a figure (which resembles a Skekis) strike the crystal. That moment is never mentioned or alluded to again.
Also when Jen finds the particular shard, what is it about that note (or set of notes) which comes to mind when he has it narrowed down to three of them?

 

[Laszlo]

If I remember right you can find the answers in the WORLD OF THE DARK CRYSTAL book.