Please allow Rachel to shatter that confidence.

The problem is, while the horse can smell another horse, and vaguely a human, it still can't see. Rachel has no idea if she's catching up with someone from Milliways or stumbled across a native.

And if she puts her bag down, she may not be able to find it again without demorphing.

Well.

She'll run faster.

And see if this person finds it strange that a very clean, strong horse is carrying an overnight bag.