Alright I'm a guy and new to this subreddit but I'll give you my 2 pennys on the matter.

I'm 20 years old and I made niyya to get married at the beginning of this year. I tried using OkCupid and SingleMuslim (Shady as hell business) and they offered quite a variety of people. I would message people that I thought had interesting bio's and were moderately attractive 50% of the time I would get a reply and if I was lucky then an actual conversation followed, otherwise it didn't lead to anything. I felt the biggest issue I was facing was people's freedom of choice..which isn't a bad thing by any means but especially somewhere on an online site where you have so much variety and options I think people are aggressively picky and some do not even consider to the Deen in this aspect when they look for spouses. Too often I would find things like "You must have this and this and so forth to be considered" "You must be of this height and you must be earning this much insert sum a year" etc. I continued to search for about 4 months until I just decided it wasn't working and the attitudes of some women towards marriage just made me quit and honestly I lost a lot of respect for these females. (That's probably because I'm salty though aha but alas).

There are four things that the Prophet (PBUH) told us to look for in a partner. Her wealth, her family status, her beauty and her religion. And out of the four choose the women who has religion above all else. And That is what I'm hoping for Inshall'Allah.

Anyways I did have a similar experience like you did. I traded a few messages with this one person for about a month and we seemed to be getting on fine, I had actually thought my search had concluded at one point and she was the one but then out of the blue she just stopped talking to me one day. I was a little baffled to say the least and honestly at the time my biggest concern was that she was safe. but yeah that was the last I heard and she never got back to me.