As you know, I have a 20's Vega Tubaphone #3 like yours and ours are a few serial numbers apart.
I stole mine on e-bay in about 2006.
I once asked Shane what happened to his last plectrum and he said he gave it to one of the road managers.
I think the last time he played one was at the 80s Reunion...the one with Tommy Smothers.
A few years ago, believe he had Greg make him one from Koa and he sold it.