Alexander Khovansky previously wrote in this discussion: "By the way, there is one quirk about user exit. Sometimes this event is
not generated, but user mask (pixel map) returned by
UserGenerator::GetUserPixels has no pixels, so user is in fact beyond
the field of view. I noticed that when this happens, user never
re-enters again and is lost after some time.
And keep in mind that NITE recycles user IDs. If you had a user with
ID=1 and it have been lost, and you see ID=1 again, it is _another_ user
(as NITE thinks)."
I suggest checking the UserPixels as well, if there is none you can wait or consider him lost immediately. This should work even when the user is detected as a new user because he moved too fast. To workaround the ID recycling, maybe you could keep track of the user position, if he is detected far from the "lost" position, it might be another user who entered the scene but used the same ID.
To be honest I have to improve this user control on my app as well, I'll try the UserPixels idea.
-Sergio