But Harry's not aware that Jugson was watching in chapter 78.

I think it was Jugson that cried for Azkaban first, which could be taken as poking.

Good point, he's described as having a scar in 78 as does the man who does the shouting in 80. However, Harry wouldn't be able to identify him (unless he looks sufficiently like his son).

But given that, I'll now agree that if Harry identifies Jugson, he might think of attempting a frame.