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.
They can't but not because of the fuels. It's because the Dragon capsule is the only part of the whole launch stack that can re-enter intact, and it's a payload to the rocket. Ther Orbcomm sat is also a payload, but a secondary one. They both get put into their correct orbits (in theory) by the disposable Falcon Upper Stage. There's no way for that Falcon Upper stage to bring anything back, it is just allowed to burn up after it's been used.
"Unfortunately, the engine malfunction placed the Falcon 9 upper stage in a slightly different approach to the International Space Station. That new approach caused the stage to violate a set of conditions known as a "safety gate"; there was no way the satellite could ascend to its intended 350km x 750km orbit without crossing the ISS orbit, and no time to check to make sure that no collision would occur. The second stage's flight control software automatically cancelled its second burn, leaving the satellite in a much lower (203km x 323km) orbit than intended. Engineers from Orbcomm and Sierra Nevada Corporation, the manufacturer, are deciding what can be done, and both SpaceX and Orbcomm are being noticeably cagey about their press releases."[1]
That said, it's impressive that they were able to make the proper adjustments and still complete the main objective. I wonder if they can bring the satellite back down, or if the fuels[2] used in the satellite prevent its return.
[1] http://arstechnica.com/science/2012/10/spacex-dragon-capsule... [2] http://en.wikipedia.org/wiki/Hydrazine#Hazards