Inverse frequency illusion
Frequency illusion or Baader-Meinhof phenomenon is a cognitive bias where after learning something new for the first time you suddenly notice the same thing all the time. But there must be an opposite to this too.
I'm pretty sure there used to be things I came across frequently in the past. But then at some point they have disappeared. I don't notice those things anymore. I'm not sure if they actually even were a thing or did I just imagine it all. Maybe I just remember incorrectly.