Ical "lost" two of my five calendars

A couple days ago, two of my five Ical calendars disappeared, and along with them all kinds of info I need for work! Those calendars don't even appear as options on my iphone or computer anymore, and of course all the hundreds of events I put in, past and future, are gone! I really need the info back as I track some health matters as "events" and I also do my billing for work off my calendar. Any ideas on how to get the info back? I'm pretty sure the last time I saw the calendars was Sunday.