A little from the car, near the road, Arnold finds a couple footprints well dug into the gravel. They aren't clear, but the fact that they are still visible at all suggests that this was probably a spot in which O-Yama dug in, and the most likely reasons he'd do that would be because of a struggle of some sort, or because he took off running at that point. If it was a run, the direction of the prints would suggest he ran down the road back the way he came.
Arnold finds that the car is out of gas, the battery dead, because the ignition key was left on. This suggests to him that O-Yama left the car in a hurry, and was also probably suspecting he might need to take off in a hurry. That obviously didn't happen, though.
There might be more to discover in the car or in the area around it, but that would require further time. The same is true of doing a larger search of the surrounding area.
in game terms, Arnold can do one or more of these searches as an Extended skill check, following normal rules for number of possible rolls, cumulative penalties for failed rolls, etc. Assume that for a car search, each roll = 2-3 minutes of searching, while each roll in the environment = about 15 minutes.