Personally, I think we should be okay with having a great conversation with a stranger and leaving it at that. Exchanging contacts isn’t always necessary. One of the beautiful things in life is being able to remember a good conversation with a random person and move on.
DON’T JOKE WITH THIS DUA: Ya Allah, remove every barrier that stands between me and the things You have written for me. If there's any delay in my rizq, in my marriage or in my peace, ya Allah remove it with Your mercy Ameen!