Sera notices something, something that the pair hadn't taken into account when they began, the Truck isn't a Hedge Truck, it's not Faerie Mount tranversing the expanse of the wider Hedge. It's a mortal truck. And it's rusting.
There's not too much that can be tracked within the confines of the truck, even if their goal would be large enough that it shouldn't matter. Circe does however see, something akin to the turn off to a cart-wide path.
Just to be clear the Spider Bazaar is a Nomadic Market that I brought out for the Plot (In Summer), it's long since moved on (As it's Autumn). Which is why I have the Market Watch plot going on, so the Freehold can search for a perminate Market and avoid all the uncertainty of a Nomadic Market.