Someones forgotten their basic physics lessons

If you launch something with a trajectory on Earth, even at hypersonic speeds, gravity still provides a 9.8m/s^2 downwards acceleration (downwards being towards the centre of the Earth naturally). Hence you will get a standard parabolic arc, as you do with any weapon.

Bullets fired from a gun follow the same path (only at much slower velocity), so your right that the object will APPEAR to have a very flat trajectory, but will indeed be following a parabola back towards the Earth... It might just take around 100 miles to do it...

Only problem i see is if your trying to hit something thats behind a mountain...