@feditips @NivReggev thanks for chiming in and explaining what’s going on. This is actually quite unintuitive for new users. I thought that only the servers store their users and toots from these users. But apparently that’s not the case and there is some form of content fetch between servers instead of server <-> client.
So in the end I “just” need to wait longer until someone from my server has boosted a toot from a user I’m interested in such that I can see that toot?