This question already has an answer here:
We know it escaped on the passenger side; however, when the cop goes back to look, all we see is a wall stretching for miles (and T-800s do not run as fast to not be able to see it running off). Additionally, it was probably trying to gather itself after taking a HUGE blow to the body (it takes time when being hit by a bullet, earlier in the movie as well as when it is throw off a motorcycle). So how exactly was it able to even get from the cop car, unseen, to the hotel? There is no way it could have slipped under anything (even under the car), with the cops not being able to find out. T-800s do not run off that fast, especially if it was injured and there were cops, with guns drawn on Reece, Sarah, and probably some on the police car as well.
Any sources from the novel or any footage that could provide an answer to this?
Edit: (This question does not ask where it went after, it is asking how it escaped..what means and where it could have slipped under?)