I think it has to do with the fact, that Paul, one of the admins, left ipernity. I don't know, why he did. And I suppose, that Mo, the other admin, did so, too. At least I can't find her anymore in ipernity. Thus - no admin, no group. That's what it reads, if you click on Mo's Foto Garten: "Diese Gruppe ist geschlossen, es gibt keinen Administrator." I have no idea, why they didn't transfer the adminship to somebody else.
Too bad ...

No, Mo is still active (https://www.ipernity.com/home/293487) and had seen this article. A group don´t need an admion or so to exist, if the last admin leave ipernity (and close the account, as well) the guy who joined first the group (after the admin) became the new admin. If the admin don´t close the account but simply leave ipernity the group stay as it was (and there are many running groups without an admin, often they don´t need anyone like this to get a healthy group). If this is the case anybody could contact ipernity staff to get the "new admin" (the older ones staying, as well, and of course, couldn´t de-opped or kicked out of the group, not even by the new "owner" so they just could came back if they want it some day).
But there´s no need to delete a working group without further discussions and that´s the point I don´t get- but well- as it seemed like Mo won´t explain it we don´t get the reason why this group was deleted...

Oh yes, she's still here. Ok, I didn't look exactly enough ... ;-)