Quote from Widow Bates investigator notes:
"Mike Castro - owner of Bowen Ranch has many stories about Ron's car and how it was found."
I can not reveal everything about Widow Bates' investigation. However, those few exerpts really shed some light on the events leading to the car being turned in by Mike Castro. It appears that when the advertisement came out asking for information and offering a reward, the ranch hands, Michelle Hart and Eric Heinrich, decided to turn in the car for the money. It wasn't until the reward elicited other people to come forward about the car that instigated Mike Castro to finally turn in the car. Mike Castro realized that Eric and Michelle may actually claim the reward and would expose the car's location that's when Mike Castro turned in the car and attempted to claim the reward.
Mike Castro suppressed the evidence of the car until the $5,000 reward overcame his capacity to control and intimidate Eric Heinrich and Michelle Hart. Eric and Michelle decided to collect the reward and turn in the car. It was shortly after this that both Eric and Michelle left the Bowen Ranch. I haven't heard about them coming back since. These two individuals have knowledge of many of the events during this time.
I can not speak for Widow Bates.