They were willing to put in a lot of effort because they were hoping for a great catch. Fortunately, their wait bore fruit a few minutes after.
The scout was able to spot Kelvin driving towards the city. Not that Kelvin was making any attempt at hiding himself. The car he was driving was hideous, and it was playing music at an obnoxious volume. Even the dead would be aware of his presence.
All these things made the tip-off very suspicious. The heroes suspected that there was a scheme afoot. But they still wanted to swallow the bait and the trap whole. So they discussed and decided to go after the bait.
A lot of vehicles came out of New London and began traveling in the direction of the diamond man. Meanwhile, the scout followed the diamond man and updated the rest of his location.
This was easy to do since the diamond man was driving slowly through the wilds. The scout could keep up with him easily.