I am level 30 and I recently began playing seriously again (like this weekend) and somehow I got signed out on the loading screen.
I don’t remember my password or even my trainer name, and it is not possible - in-game - to retrieve a lost password unless you give other info like trainer name, screen ID, date of birth etc, so how can I start playing the game again?
I have contacted Niantic support but who knows if they actually bother reading.
To me has happened the same, when I was at level 28. I started again with a new account, and now I’m at level 35. So, take it with patience, start a new account for having something for to play with (in tthis moments the never visited Pokestops give 2100 XP, a very good way to start again). And if you get access again to your account, even better.
Dont you get a confirmation Email when making an PTC account? Maybe your trainer name is in there.
Also in the future it might be a good idea to take a name that means something to you, so you dont forget it. And fill out your actual birthdate so you cant forget it.