My Canadian Passport was stamped C1! What does this mean?

I have a problem that's been worrying me a lot. I came into the US using just my Canadian Passport by air, stayed a month and then left to Canada and came back overland. At the border, I explained to the officer that I was taking a course in the faculty of continuing education at a university in New York, which does not require a student visa. She grilled me about this, and stamped my passport with a C1. I'm unclear, can I stay the remaining 5 months allowed to me as a Canadian, or only the 29 days usual to a C1 visa?

-- Mon Oct 18, 2010 12:53 pm --

I've actually figured it out, the C-1 stamp was for a previous transit through the country, and so does not apply to my current situation. However, I don't think I was issued an I-94 form. If I was, I've lost it. Do I need to have it replaced, or is there some other way of finding out when I need to leave the country by?