Here is the story for those who are interested:
I met this ENFP guy while travelling via coach from Berlin to the UK. We started chatting while crossing the English Channel and he told me that he had just finished studying Linguistics in Cambridge and was a vegan and a very active environmental activist who supported countless different causes. (Just our reasons for taking the coach instead of flying were very poignant: I took the coach because I was moving back to England and had so much luggage that that was the cheaper option, he took the coach instead of the plane in order to lessen the carbon footprint... I guess I am far more of a pragmatist.) We got on really well, talked for several hours about language, how it shapes your perception of the world and our country, environmental issues etc, he was just somebody that I felt I could really learn something from (despite him being a few years my junior) and someone I could open up to very quickly.
We arrived in London around midday and I had a few hours to spare so he offered me to come to his parents' house and I thought: "Why not?" So we chatted for another hour on the bus to his house, he was a complete gentleman (his EQ was a 10 out of 10) carrying my luggage etc, I met his mum who gave me some vegan soup

and introduced me to their sausage dog and they both pored over the newspaper of the previous day, which included an article about some environmental activists bringing a runway in London Stansted airport to a standstill (who of course turned out to be my little lingust's friends

) It was just a gloriously random evening.
In passing he mentioned that he had a girlfriend (though I am unsure how important your gf is to you if you willingly spend several months apart from her and instead prefer to travel all over Europe trying to save the world), so I thought I would still like to stay in contact on a friendship basis and he encouraged me that he would give me the details of one of the environmental meetings this weekend, if I would just contact him via email. So I added him on Facebook, he accepted the invite and then I sent him a message concerning the meeting.
And from then on I didn't get any reply. I contacted him via Facebook and via email and I sent him a text message (and one wishing him a Merry Christmas) but I didn't get any response at all so I thought: "He is obviously not interested in keeping in touch and I really don't have the time and am not willing to run after him. End of story." I left it at that until two months later out of the blue I got a message on Facebook from him saying, how in the last week he had regularly travelled through the station where our coach had arrived at, and he had been thinking of me repeatedly and was wondering how I was doing. I thought: "WTF??" but sent him a friendly reply, telling him that I would be happy to accompany him on one of his many campaign trails. And since then I haven't heard anything from him.
To me that is just a bit of a mystery. How does the ENFP brain work?? I personally respond to most personal messages I receive (especially if I have been contacted several times by the same person), mainly because I don't want to hurt the other person's feelings by ignoring him or her. I also wouldn't just ask someone out of the blue how they are doing, just to disappear again completely while not bothering to respond to anything. Especially in a very busy city like London I very quickly put people like this "ad acta" since I really don't have the time to play around, either you are interested in keeping in touch and put at least some basic (even if irregular) effort into it or you are gone.