She was curious about how Xiao Xu found him.
When the police seized her phone from the suspect and returned it to her, it served as the answer.
On her phone, there were booking details and call records with fellow townspeople. How could Xiao Xu not know after checking her phone? Moreover, in the phone settings, Xiao Xu had access to her phone's location.
Thus, from the moment she left Beijing, her whereabouts were within Xiao Xu's scope. He even took the same train as her.
Fearing she might get upset, and wanting to surprise her, he didn't reveal himself. He planned to show up in front of her at the best moment after reaching the destination, but unexpectedly, things went wrong halfway.
She took the bus, whereas he rented a car, following the bus from a distance since he knew the direction she was headed. However, there was a traffic issue about ten kilometers away from a service area. Two cars had rear-ended each other behind the bus, causing temporary congestion.