In reply to Removed UserBoingBoing:
happened to me once, after ringing the British Consulate in Paris, I went to the consulate, filled in an application for a replacement (which included a statement that I had lost the old one, luckily I had a note of its number & issue date) which I picked up a couple of days later. That was some years ago when some consulates & embassies issued passports, I guess now you just apply on line & make sure you fill in the section explaining why you can't produce the old passport.