Luzula

Yes! Andrew Lang suggests in his book that Scott may actually have known who Pickle was, but refrained from saying anything publicly for the sake of his friend:

A friend of Sir Walter's, a man very ready with the pistol, the last, as was commonly said, of the Highland chiefs, was of the name and blood of Pickle, and would have taken up Pickle's feud. Sir Walter was not to be moved by pistols, but not even for the sake of a good story would he hurt the sensibilities of a friend, or tarnish the justly celebrated loyalty of the Highlands.

I have not read any of the Porters' books yet, but I definitely intend to try the one about Jacobites at least (The Pastor's Fireside by Jane Porter). There's also one about much earlier Highland history, The Scottish Chiefs, which I may read if I like that one!