I think the Grindr app should have a filter to only show people you haven't chatted with yet or only people you have already chatted with. Just like there is a blue indicator on the user's profile that says chatted and the minutes and hours in 1 day, there should also be an indicator on that user's profile that just says chatted and it should be in a different color than blue and should stay on that user's profile to let you know you have already chatted with that user, since the blue chatted (minutes/hours ago) indicator will go away, there should be one that stays on the user's profile.