I do hope you get back your ipad.
However, I hope the following info will help others who read this post.
For future use there are a couple of apps that can further assist you even if find my iphone/ipad is set up and on. One is gotcha in the itunes app store. A story is here which also shows some alternative apps you can use in addition to find my iphone/ipad.
http://www.huffingtonpost.com/2012/12/11/iphone-thief-photographs-herself-igotya _n_2276613.html
Last year it was on the news when a similar thing happened in our city. The guy got caught. About a year ago, someone posted here a thread entitled something like find my iphone works! He was also on a flight... seat pocket...back to plane... cleaned. He searched it on another computer. The phone was off and then turned on...on highway. The person was driving home and the owner kept track. The ipad owner used Google Earth and located the name, address, and phone # of the person when they got home. The owner called (?) the airline employee who had his ipad, told him he know he stole it from the plane and told he would send people after him, report him to his employer and he would not be allowed to work in that field again, OR he could mail it overnight to the owner. and he would not contact law enfor...or report him to the company. A day and a half later the owner received his ipad in the mail. (Personally, I'd then have reported him and had him fired. It probably was not the first or last time the guy was going to steal from a plane.)
I think you should get on Air Canada's case and insist they and hopefully all put an end to this. It's bad enough that this goes on quietly with checked luggage, but on the plane? At the very least all stewards on planes should remind all over and over again to 'empty their seat pockets and do not leave without your ipad, iphone, laptop, etc.' The mention of those words might help.
And airlines should ensure that everything the maintenance people do on a plane is videotaped. And as they leave the plane, they should have to go through security checks - there and then! (Before, too!)
People on a plane have paid good money and should not expect this to happen.
I hope you find your ipad!