Help. I booked my flight through a travel agency for my AIR ASIA flight...?

.... and they sent me the BOOKING CONFIRMATION on the same day, but it does not contain my passport number. It only contains my flight details, flight number, departure and arrival dates and timing and the confirmation number. But doesn't a travel itinerary has to have a PASSPORT number, so they know the identity of the person who's traveling when checking in? When I asked the agent, he says its fine, but I'm scared that they might stop me at the airport! Do they really not have the passport number on airasia travel itineraries?? I know that all major airlines have it. Help?