You could also hang posters at the local supermarket, ask if you can leave one at the post office etc.
When I was younger, our cat went missing once when he still was very young (he was jet-black, too). Someone saw the poster at the post office and contacted us. Our cat had moved into a pub!!!

I so feel for you and especially your DS. I hope you find Ruby.
If indeed cats are beeing baited, how awful. I cannot understand how someone can do that.

Sasa