Events not appearing in iCal (iMac)

I create an entry called 'Cancellation' when I have a space in my diary so that I can search them easily in iCal. However, they are not all appearing in the search. I've tried copying an event that does appear in the search, and I've tried creating a new event. I've checked the spelling is the same. But these new items are just not appearing in the search. I've quit iCal and started again. Any ideas?