We always used to go up to Torch Lake during summer when I was a kid. Collected a bunch of these. The easiest way to find them is to bring some water with you and go for a walk on a rocky road, and pour the water on likely rocks. The water makes the pattern much clearer and fewer people look for them on the roads.
Bayesian statistics says the opposite. By looking at the history of an entire city, you're giving yourself a highly uninformative prior. This means that it's very difficult to actually draw conclusions from the results. You have to reduce your population size first, and then perform your "test" (looking at search history) on the subset of the population who actually has a reasonable chance of committing the crime even without the search evidence.