Yeah, I've had a lot of friends who've forgotten about me. I do my best to maintain a close friendship and open communication with them, though, but I think the reason why it happens so often is because there's a lot of misunderstandings between our group of friends.
There's this one girl who was a bit of a loner in the beginning of the school year. We'd always approach her and let her sit with us in the canteen, let her come with us on random adventures so she wouldn't feel left out. She was pretty happy about it, but after some time, she started to talk to the other girls in class. At first, we were okay about that, because that means she's opening up and socializing more. It's not like we're the only friends she could have, right? So this went on for, like, three months, and after that, she completely stopped hanging out with us. Then a month passed, and she started following us again. We were honestly very irritated about that. We'd always think, "Why is she hanging out with us again? Doesn't she like her new friends?"
As a tradition, us friends would have an open forum at least twice every month, so that our friendship would be stronger and we could let go of any negative thoughts. We did that once and included the girl, so we could finally confront her about it. She told us that she didn't hang out with us anymore was because she felt like we were just being fake towards her, like we were being forced to hang out with her because she was a loner. After that, we started to loosen up a little around her. It sort of proved that communication solves everything -- or at least problems involving friends.