Posts vanish after I read them EDIT: Solved

Hi, today I noticed that posts vanish after I read them. Like: I click on a post, reading it in a new window, then jumping back to my "timeline" - but it's not there anymore.

Is there a new option "hide when read" or sth like that? I am quite confused, I did not change my settings lately, but this behaviour is new to me. Help and / or an explanation would be appreciated!