As all practitioners of a (semi) regular routine of unplanned or automatic drawings can tell you, making a genuine “lucky drawing” is a rare event. I’m honestly not sure whether the term is my own invention or not; it’s quite possible someone taught it to me, or just talked about it in my presence, so long ago that I don’t even remember ever not knowing it. (If that someone was you, thank you very much.)
A lucky drawing, as I (loosely) define it, is a good drawing that just happens. There is no thought or planning, no blocking, no pencil underdrawing– just a single stroke* with an ink pen or a brush, and then another, until the subject is suggested and the drawing can be finished. That is usually fairly quickly, especially when working with the brush– most brushwork lucky drawings take less than fifteen minutes to complete. If you work too hard on a drawing like this, you may get a good drawing but it won’t be lucky. Ideally, a proper lucky drawing also requires no corrections, although I allow myself to white out the occasional early line that turns out to be misplaced if I can do it without disturbing anything else. There is one such correction in this drawing, but I won’t tell you where it is.
As for the Wolf Angel himself, your theory is as good as mine, but my guess is that he is a minor saint or godling, perhaps one who watches specifically over werewolves and those who love them.
*In this case, the first stroke was the line under the Wolf Angel’s chin.