Hi, Jazzyvee!
Fortunately, I never had any damage on my bass during a jam session, and I don't have any scary stories to tell, but the point is that I was feeling a little nervous when a bassist I didn't know was taking my bass to play with. And this was before I bought Ambre, my 5 string MK sig.
Now I have an Alembic, and I'm a little like you, I have never left anyone play with her during a jam session. Some of my good friends have tried her, but not at a jam session( in my place, at music school,...).
And the other point is that I don't know how I would react if someone was damaging the bass I've been dreaming of for years and years...