There are a couple things to consider.
1) None of the current trail cameras use a "trip beam" to trigger the camera, so there is no projected light, IR or otherwise, for a sasquatch to see EXCEPT when the flash is happening. That is an assumption based on decades old, decades-abandoned, technology. The only chance they'd have to see light, IR or otherwise, from the camera is when something else is getting its picture taken.
2) Cameras have plastic bodies .. probably out-gas.
3) Cameras have batteries and capacitors. a) Capacitors make noise .. some humans hear them, some do not .. when they charge. b) Some people speculate BF can detect electrical fields.
4) I've done some experimenting .. as seen by an IR camera by IR flash, our "camouflaged" cameras are plain / bland square, artificial-looking boxes on the sides of trees, not camouflaged at all, so if BF sees in IR, our cameras are probably glaringly obvious and out of place.
5) I'm a hunter. When I hunt, I don't walk down the game trails, I walk 25 - 200 yards off to the side so I can see without being seen. Most all of those bajillions of trail cameras are set watching the game trails, not watching the woods for things watching the game trails.
6) BFs are tall. This, too, would lead them to walk in different places than short critters like deer walk.
7) Most hunters do not leave their trail cameras out year around, they're only out seasonally.
8) Cameras require visits to change batteries, swap SD cards, plus putting them out and picking them up. I usually only visit mine 1-2 times a year but hunters often go back every week or two. That's a lot of tracks going to an otherwise nondescript place for no apparent reason and even if a human maybe doesn't notice them, a sasquatch might well. Plus scent.
I think the odds of a picture taken by cameras set up for deer / elk / etc instead of specifically set up for sasquatch don't have a lot of chance. Groups who are using trail cameras specifically for bigfoot research have a better chance but IMHO they need to do a better job of hiding their stuff and they need to leave it absolutely alone for longer periods of time rather than having their curiosity draw them to the camera too frequently.
People think that numbers are the answer. Numbers don't matter if ineptly or inappropriately used. Those cameras are just clutter. So how many are really useful of all those millions? A few hundred? Maybe 1000? The rest are relying on luck.