Police have always sought information. They sometimes knock on doors, or put signs up at the roadside for passing motorists who may have witnessed something, or put out media appeals. And now they use social media. So what's the big stress? Policing in GB is largely by consent, and asking the public to support them in upholding laws passed by democratically elected representatives is hardly asking us to do their jobs for them. The assumption that if 'someone other than a resident saw it then wouldn't they have been interviewed at the time?' is just that, an assumption. If they don't ask, they won't know, will they?