Ash:

When you used your passport in the past did you give the number to your travel agent? He or she might have kept a record in your file.

I hope your passport comes back soon - this has to be very frustrating.

I know you'll make copies when it comes back - one more hint - laminate one of those copies and carry it with you when you've on shore during your cruise - the cruise line usually collects passports when you're onboard (not on all itineraries, but in areas where passports are needed to clear ships into other countries) but the copy helps if you need it when touring etc.

Often you need you passport number to fill out disembarkation forms etc. too. I'm always glad I have a copy handy.