Contact the US embassy as a matter of urgency. They will be able to advise you and help you to get a replacement passport.
If you were born in Canada, how did you get a US birth certificate in the first place???
As long as you are considered a British citizen, you can apply for a passport. Contact the British High Commission and check if you have not lost your status.
If it's operations are anything like Austria's, you should contact the Romanian consulate general or embassy in London. I was able to get an Austrian passport in Canada this way.
You must have reported the passport lost so that you may be able to Apply for the resplacement. Your passport number could be used to verify some information about your passport.
If you have lost your passport, you will need to fill out Form DS-64. It can be obtained from any Passport Agency, or you can print it from an online web site.
Answering "Your passport got lost can you travel with your ID card?"
Sorry, but unless you have a copy of the data-page of your lost passport, there are no ways to find the passport number, issue and expiry dates.
You can't board a plane when your passport is lost. Go to the nearest embassy of your country of origin and get a replacement passport.
It depends why you have lost it.
Usually a cancelled passport is due to Death of the owner of the passport, or if it is reported lost or stolen and is replaced with a new passport.
I would recommed you to first report a lost passport. Following website has list of countries and under them are procedures which can help you out. Website : www.wikiprocedure.com
There is a "Passport Card No." on the top right on the front of the passport card. But it has nothing to do with your passport booklet. You should notify the police as soon as possible.