I'm happy to report a happy ending. Scamp returned home today.
This morning I was up early for work and was out for the day. I had seen some emails that something was recorded in the garage. As it turned out he had been lingering in and out of the garage early in the morning and as late as 6am. I was kicking myself for not looking at the video earlier, as he was in the garage while I was getting ready for the day. So knowing this, and based on a recommendation from the Oakville and Milton Humane Society, I left the garage door propped open, along with the door into the house and the rear door. As expected, my furnace was none to happy, but Scamp eventually walked in.
All day I felt pretty bad that I was out and he was so close. Thinking he might come in and then leave again because the doors were open. As it turned out, I came home called for him and didn't see him. Well the dog was itching to get outside, and do his thing. Came back in, called again, and there he was peaking out at the top of the stairs inside.
Apart from having lost some weight, and some slight redness on his forehead, he seems ok, but obviously tired and probably full of stories for the next day or two. I'll get him checked out at the vet in the morning to be safe, and i'm sure my checking account will not really appreciate that

So what i've learned is this. Indoor cats are not likely to roam very far. They are not used to the outside, and apparently will stay close to home. They are likely to be on your side of the street, and hiding under bushes, a deck, furniture, bbq cover etc. OMHS said it was very important I conduct a door to door search of neighbouring properties. Two nights ago I did this, and many of my neighbours, whom I had not met before, were on the most part receptive to letting me into their backyards to look around. One neighbour was absolutely positive she had seen him that afternoon on her back deck. So this renewed my hope that he was in fact close by and not some coyote's dinner. The following day I searched all around and didn't see him. Thankfully for me the motion detection on the surveillance cameras worked.
If anyone is wondering, and think they would go this route, it took only one of the cameras. I used a D-Link DCS-933 that was wireless and set it up in the garage, and it recorded to a DNR-201L Network Video Recorder with an attached external hard drive. Now the setup isn't too hard, but I work in technology and got it going. It's not Mac friendly, but it accessible through a browser. Works better in Windows. I received email alerts everytime something was detected and that is when the camera's started recording.
I'll be making a donation to the OMHS, as it was them that provided a lot of the info I used to base my search, and the tip to leave the doors open. They advise that an indoor cat is likely to come home if it can find its way back - they suggest putting out the cats litter to help them reorient themselves and detect their scent. They say to leave the door open that they likely exited from, and this gives them the opportunity to sneak back in. If they come home and can't get in, they will likely keep roaming around, and hopefully it isn't too late at that point. The longer they are out the higher likelihood they will wander off further, and then be difficult to find as they could be anywhere. In one major block of homes that could be close to a few hundred, and a logistical nightmare to search.
I know not everyone is going to care about this post. I've seen them all the time. But I didn't realize what was really required to find them. I will admit the prospect of going door to door and expecting everyone to take you seriously seemed a bit daunting. I lucked out thankfully. Hopefully this thread will hold some tips for others in the future. Here are some numbers to keep in mind.
Oakville and Milton Humane Society -
http://www.omhs.ca - 905-845-1551 - They will take a lost report, and contact you if anyone reports the cat, or if they come in contact and they are able to identify your pet if they are chipped.
Milton Animal Control -
https://www.milton.ca/en/live/animalcontrol.asp - 905-878-7252 ext 2254 - they will take a lost animal report, however contract out their lost or found pet pickups to Burlington Animal Services
Burlington Animal Services - 905-335-3030 - They do not take lost cat reports, but would track anything that comes in from Milton as found. Make sure that you file lost animal reports with OMHS and Milton Animal Control.
24PetWatch -
http://www.24petwatch.org - 1-866-597-2424 - If you have your pet chipped, and have the info, you can call them with the ID number and they will take a report. They advised that Milton, OMHS and Burlington Animal Services, along with neighbourhood vets all have the ability to scan for a chip, and report a pet as lost or found. They also did mention, that if someone found a pet and decided to keep it for themselves, and happened to take the animal to a vet for a checkup, if they admit the animal was found, vets will scan and report the animal as found.
I followed up with all of these to advise that Scamp had been found. It is nice to know that they are around to support you and take you seriously.
Thanks to everyone who showed interest in this post! Have a great weekend!