If you do manage to get your book of paper matches wet, I've found by experimentation that you cannot successfully dry them out - the match head becomes crumbly and brittle and will not strike, period. However, even if the match head has been completely washed away, there is still some of the material embedded in the paper tip. I've tried lighting this with a small magnifying glass (such as the one in the SAK Champion). It does ignite, though there isn't enough of the material left to actually ignite the paper match; in extremis, I would probably not even attempt to light a single match from such a book, but would probably try igniting the entire book.

If the book of matches is in a "waterproof" container that is flooded, I would also try straining the entrapped water through a tissue, letting the tissue dry, and then use that a firestarter (in the hope that enough of the dissolved match heads would remain as an accelerant to improve my chances). I always meant to experiment with these ideas - maybe the next time I do laundry ... <img src="/images/graemlins/cool.gif" alt="" />