Do they need to find out about it or just a way to participate in it? If the first, make it something that can be discovered through reading the paper or a forum. Missing persons databases or websleuths? Maybe they heard a noise and call a tip line? Or they notice some clues that people who don’t regularly read the paper from cover to cover wouldn’t notice? Or they’re an expert in some thing and the detective contacts them?

If the second, can they do the research online? Make the costumes/props for an investigation (think Sam and Dean’s FBI badges)?