I don't know if I would put money on that. Even if most of the country has been explored (I would never say thoroughly) there is a LOT of territory that is extremely desolate, especially here out West. There's also a lot of Canada that's exceptionally remote too. Just because a person's been there doesn't mean people go there very often and wild animals tend to be a little on the elusive side.
I would have to agree. Even in areas which are populated there are some unexpected creatures to be found. Here in Scotland there aren't meant to be any large cats, but that doesn't mean they don't exist. And if they aren't meant to exist then very few folks actually go looking.
I once saw a Caracal jump over a 6 foot tall bush on the way to the pub between Newport on Tay and Wormit whilst walking along the nature trail (the old disused railway line running behind the village). I suspect that there are even larger cats in the more remote areas of Scotland having come across tracks in the snow. Cat paw prints about 20cm across.
Just look at the effort it took to get some video of the Snow Leopard in Pakistan.
http://www.youtube.com/watch?v=Wp3KTK4kHII&feature=related