Thanks for all your help guys, thankfully, my bag was found today. By of all people, a policemen, who was kind enough to look at my luggage tag and called my cell number. It was found behind the staff area at the gate, and its been sitting there for the last three days. amazingly the only things missing was some coins from a few different countries that i decided was too heavy for my wallet.

What i think happened was because the luggage elevator at the DTW C38 jet-bridge was full, the luggage agent put my bag beside it (thinking that he would come back for it, but instead forgot about it. And when the plane left, the ramp agent took my bag off of the jet bridge, and didn't bother doing anything about it, and in the last 72 hours none of the countless agents who worked at the gate bothered finding out who that unattended piece of luggage belonged to. I always thought this was a possibility, and I've asked the luggage agents at YYZ to contact gate C38 at DTW to check for my luggage, but it clearly wasn't done.

I guess the question now is whether get delta to give me some compensation for my ordeal.

This experience really got me thinking about the security of gate-check luggages. like peachfront said, a passenger could easily pickup someone else's bag and walk right out of the airport. If he was smart and kept an eye on his mark's seating place on the plane, there's almost no way he could be caught. (thankfully this couldn't have applied to me this time because i was the first off the plane). Also the fact that gate check luggages aren't properly tagged simply makes searching for them next to impossible.

And a reply to peachfront, there was no way i could have carried the items that wasn't covered my the airline without breaking the airlines rules. The laptop, camera, and travel documents bag (which i couldn't have replaced with my pocket because it contained some business documents as well) would have all counted as their own "personal items", and i don't think a $400 noise canceling headphone is of little value, plus in this case, i also had two extra camera lens. The idea is that you would be able to hang on to all your items in an emergency so they don't become flying projectiles, and there was no way i could have done that in this case. I guess the lesson here is never to put too much trust in an airline.