You don't need to roam the streets, but on monday or tuesday I think between 20:00 and 24:00 if you go to the residential area appears a new option, something like lovegood lane.
It's not an RNG event and as far as I know 5% is the lowest probability, so, for future events, if after 5/10 times you repeat the same thing the event doesn't trigger, is safe to assume that something is missing.
I suggest you to save before entering the lane and try all the options up until you end the quest, since there are two more or less interesting scenes, but they are mutually exclusive (if you want spoilery details I can give them to you).