Oops, found another "speciality" in LR2:
I had just flagged out some images as "rejected" because they turned up in a "smart-collection" but didn't belong there: They were some jpgs without any additional development so I just wanted to keep the corresponding NEF-file.
1. pitfall: if you've identified an image for deletion in your LR
collection and do the right-click-boogie: There's no option to delete the image from the data-base or the computer. This has to be done in the "Folders" section of LR. You can only "remove from collection" in the collection section.
2. pitfall: now I though "easy" just select your top folder (like "images") and then set the filter to "rejected photos only" to see the ones I've marked "rejected". Well, no luck then

I searched and searched and found out that the
filter does not show stacked photos that are not top-of-the-stack

So for this search/filter to work, you have to first expand all your stacks (which might be your whole database if you're stacking JPGs with NEFs)
Now some call this a
feature - but I call this a
bug 
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Thomas (beware: Nikon-fanboy and moderator!)
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