Sometime you have to keep in shape, but you cannot bring your instrument. The only option may be the mouthpiece (it is easy to take with you in your pocket).

What do you do then?
I would bring my mouthpiece.

Actually I did that in April this year, when I was away in Spain for a whole month. When coming home in May I had gigs. So, I would go along the beach every day, taking the mouthpiece out and playing different nice tunes that I remembered or heard. After a month when I finally could put the moutpiece into the horn again, it sounded good and the range was there.
I had lost a bit of endurance, that was all. If you know that the mouthpiece buzzing is different from the playing, I think you can be fine.
Bud Herseth, Doc Severinsen, Jim Thompson, Håkan Hardenberger etc., etc. buzzed or buzz their mouthpiece.
Arnold Jacobs would have students do mouthpiece buzzing – but he wanted them to play melodies, not just exercises.