Firstly, Bugger.

Secondly, do check E Bay regularly.
Hasn't worked for me in the last two years, after my Fylde guitar was nicked, but I still regularly check.
I have heard stories about people retrieving stolen instruments on E Bay.
And E Bay are very helpful, if you talk to them.
After all, it's in their interest to keep their site as clean as they can.

I wish you luck.
The good thing is that it sounds like a signature instrument, making it more recognisable.
Keep spreading the word.
If you have photos of the banjo, publish them.
Send them to all possible shops, police, anyone you can think of.

As I say, I still check E Bay, but no luck as yet, but I haven't given up hope.

Best Wishes

Ralph Jordan