disappearing posts (db o.k., but not per wp webfront)

I successfully imported 137 posts from Blogger inclusively comments. Now, I started to give them titles and put them into categories… but suddenly posts disappear. Take a look at
https://www.iroke.de/wp/?p=41
It’s there, right? The category list in the sidebar doesn’t list “history” as it should (the article is categorized there). Looking at the wpadmin category list, I see “history” and “1” article assigned to it. Looking at the post lists, I try to search for containing words (or any words at all), nothing comes up. The search form on the weblog itself doesn’t work either, but that’s another issue I’ll have to look later into. ??
Anyways, there’s no article number 41 within the webinterface (I can see 40 and 42 though), but looking per phpmyadmin into the database, I see it. What happened and how can I get it back – also, what should I do to prevent this from happening in the future?