Refocusing, I could see the outline of the log cabin ruins beneath the snow. A quick reconnoitre and we found another cabin footprint nearby. I was not surprised to see them as that area was home to railway building camps in the late 1800s and some light logging in the early 1900s too.

So I contacted the park archeologists in Calgary to see. They had me double check the inventory and sure enough... they weren't listed. After a few back and forth emails, it was confirmed! We were the "discoverers" of these two cabins. Very exciting!
Unfortunately we didn't take pictures that day, so this is a photo pulled off the internet that is something like what we saw.
At some point, I'll join an archeologist on a return trip to document the cabins. But most importantly, what a treat it was to provide at least one set of guests with an unusual and satisfying national park experience!