Yes there is
always a tracking number on the receipt for parcels sent in Canada. If the other person said there wasn't, then they lied to you or did not know. As for who is liable for the loss, it's questionable. If the person receiving each item pays for the item shipped to them, you might be responsible.
Chart from Canada Post on different rates and features of shipping within Canada:
http://www.canadapost.ca/cpo/mc/pers...rvices.jsf#Cda
I'm not sure of the details of your trade, but if each trader pays for their own shipping, the sender should be responsible for recouping the costs to the other person or mailing back the item that was traded from their own pocket (Hope that doesn't get lost).
How big was the box? If boxes are small/thin/narrow enough, some people may be cheap and just mail it as a lettermail to save on costs.
Sadly items do get lost, even if it is a very small ~1%. Perhaps the sender wrote the address very sloppily or someone in the processing plant had sticky fingers. If there's no tracking number, they mt may have been sent as a letter or something's fishy.