'Powder room' for a home bathroom sounds a bit odd to me as well. We call it the guest bathroom or a half bath.
As for prepositions, watch out for 'auf der Toilette' as well, which in German can mean (if I understand correctly) 'in' (the bathroom), not just 'on' (the pot). (*f5* As I now see that Hein has said.) I could have sworn there was a very recent thread on that (as in during the last few weeks), but I can't seem to locate it at the moment.
As for the archive, not really secrets, but a couple of tips: Use the keyword index, not the regular dictionary search (that is, until the LEO team gets all their software and hardware problems solved and is able to re-connect the two search mechanisms from the dictionary interface, which is how it once worked for a while, now alas only a wistful memory). If that fails, remember that some entry words are misspelled or a related form is used (and the asterisk wild-card search currently only works from the dictionary interface), so check the alphabetical list of keywords beginning with a certain letter. (I keep a link like http://forum.leo.org/archiv.ende/a.html
in my bookmarks and just replace the letter as needed.) If that fails, feed the internet search engine of your choice with a key term or two that might appear in the full text of the discussion, plus 'site:.leo.org.'
And if all that fails, just say, I did try the archive but I didn't find anything. Believe me, after this many months of persistent problems at LEO, in which from time to time large chunks of the archive have either completely disappeared or emptied out to the infamous 1-1-70, everyone will understand only too well. (-: