There were a few publicity things that the devs did around launch. The game was featured on the App Store. And there were about 50k people playing at one point, I believe. The game doesn't stick with most people.
It does, however, have a dedicated following from a very specific type of gamer. If the devs are going to do more advertising, it would have to be very targeted advertising.
I think a game like this does best with word of mouth, though. It's a niche game, but I'm sure most people know at least a few others who would try and love it. Maybe that's just my experiences, but I've gotten 3 people playing this game myself. They'd have never tried it if I hadn't suggested it to them, I'm sure of that. If everyone who loves the game now does that, we could see 18k more players.
"Can I make a suggestion that doesn't involve violence, or is this the wrong crowd for that?" -Hoban 'Wash' Washburn, Serenity