Sometimes strangers are just strangers. Sometimes when the NYT reports that a congressman has been sleeping with his pages it means that he was overcome with boredom while trying to get through a printout of the budget. I wouldn't bet that way, but it has probably happened.
Pick a likely verb, for example "asked", then look at the kinds of situations where "asked a stranger" comes up. See if it makes more sense for them to be a) a bystander who we couldn't track down but, nonetheless, are sure has no pre-existing relationship to the person doing the asking or b) a NYT reporter.