Friend list issues

Alright, I'm posting this on this board because I'm not really sure where else, though I don't know whether this is really a bug or not. So the problem I've been having for quite some time now - there's a few people on my friend list that seemingly just vanished. Looking at their match history, I can see that they've actually been playing league pretty regularly, which is weird because they're still displayed as level 30 (impossible given how much they've played) and are constantly offline. Looking them up on LoLking and op.gg yields no results, either - no games are loading. I initially thought they blocked me for whatever reason, but checking LoLking and op.gg leads me to believe that's not the case. Has anyone else ever experienced something like this? If so, how did you go around fixing it? Is it just a display bug? Thanks in advance!