It can't come back down for several reasons. Besides there being no way to bring it down, it's already been released, and is basically on the other side of the planet now.
Anyway, it's a prototype satellite; OrbComm is making dozens more, and took the opportunity of a discounted secondary launch to test their new hardware. Probably having the thing in any orbit is good enough for their primary objective. I'm sure they would have liked to be able to integrate it into their eventual constellation, which is probably impossible now, but they knew the risk of flying secondary (to the ISS!) and likely found it acceptable even if they didn't get the right orbit.
Compare track of ISS vs OrbComm OG2: http://www.n2yo.com/satellite/?s=25544 http://www.n2yo.com/satellite/?s=38847
Anyway, it's a prototype satellite; OrbComm is making dozens more, and took the opportunity of a discounted secondary launch to test their new hardware. Probably having the thing in any orbit is good enough for their primary objective. I'm sure they would have liked to be able to integrate it into their eventual constellation, which is probably impossible now, but they knew the risk of flying secondary (to the ISS!) and likely found it acceptable even if they didn't get the right orbit.