Yea definitely seems to be luck of the draw from all the stories I've read. Perhaps flying is easier that driving since it doesn't look as permanent (you can't bring much with you at all and you have no car). Either way I did dig this up:
From page 5 of the guide for applying to extend your temporary status:
"If there is no stamp, a handwritten date or document in your passport, your temporary resident status will expire six months from the day you arrived in Canada. If you were given a visitor record, student or work permit, the expiry date is marked on the document."
http://www.cic.gc.ca/english/pdf/kits/guides/5551E.PDF
Looks like I'm good to go despite what the border guard said...