From Winnipeg Free Press about a week ago:

"A Winnipeg angler had to spend the night in the wilderness last Friday after he could not find where he had left his canoe in Nopoming Provincial Park after spending the day fishing. Lac du Bonnet RCMP officers in a helicopter found the man, 50, uninjured and in good health late the next morning. Police said yesterday that the man had become lost after canoeing on Mink Lake and walking to another lake to fish. When he returned to Mink Lake, he couldn't find his canoe. RCMP said the man phoned 911 on his cellphone, but when officers could not find him using GPS tracking, he was forced to make a temporary shelter and build a fire."

(Nopoming adjoins Woodland Caribou PP on the Manitoba side)

I wonder if his canoe was where he left it.

The case for a GPS and a SPOT. Not to mention some memory pills (I have some, but I can't remember to take them).

I carry a couple of rolls of orange surveyor's tape in my day pack.
Marking your trail in unfamiliar areas is more than a prudent idea ;)
Not as hi-tech or glamorous as SPOT or GPS, but will get the job done.
If you take a compass heading to the lake your heading for, you can easily take the reverse route. An orienteering compass makes it super simple.

All great suggestions.

One more.

Tie your canoe up.  I know of a couple trippers that have had theirs blown away.