Put another way, they were informed and warned about conditions by forester Pashin. They took it under advisement and elected to complete their hike. This is all mundane if they had survived; easily forgotten. It should have been straight forward. We would not be here if it were.
Instead of the extraordinary, perhaps an ordinary sprain caused Igor to abandon his boots, abort crossing the ridge. It is the endless what if's that tease at the why of it, as much as the how of it.