Bourgeois 2nd Movement added part?

[ttf_Noahharry]

I'm not sure if this fits here, but this was my best guess.  One of my favorite moments in our entire solo repertoire is within the 2nd movement of the Bourgeois and i'm not even sure its ours haha.  Nearly every professional recording plays it yet it isn't actually in the trombone part, or at least the one I own. I've found the score online and it seems to be in the trumpet part.  The part I'm thinking of really starts around here: https://youtu.be/zRhcssrbVPA?t=12m38s

So are all of these professional players just transcribing it into their part because it is killer or is there some version with it included? Thanks!
 

[ttf_Le.Tromboniste]

If I recall correctly, the edition I have has it ad lib.

[ttf_Le.Tromboniste]

If I recall correctly, the edition I have has it ad lib.