But why would we (the Army) care? If reports are made by family members who were in in areas approved for recreational use, has there been any harm or threat of harm? If not, no military interest. Even if it were a known animal (bear), the Base Commander would only care if the animal was a threat to the community (foraging in populated areas or areas approved for recreational use) or a threat to military operations (destroying vehicles, outbuildings, interfering with training, etc.). Any number of known animals (deer, bunny rabbits, bear, elk if in that area) are probably killed by being in the wrong impact area during aerial gunnery (Lewis is a joint base w/the Air Force base next door now, + the helicopter brigade), artillery practice, tank gunnery, and crew served weapons (mortars, heavy machine guns, etc.) ranges.
As to rifle ranges, the concern would likely start and stop with the question of whether people, whether military or civilian, were downrange. If a 'Squatch ambled across the M-16 range, they'd likely hold fire just because no one wants to take the chance that some clown is running around out there in a rented gorilla suit.
When one gets to even a medium level of responsibility/authority in the military, one develops a good CYA gene. So if one were reviewing or approving a Report of Investigation concerning the destruction of a B-hut (plywood hut used to house Soldiers out in remote training areas) by blunt force, even if very large footprints were present in the mud, it would be written up as an apparent "act of nature" or vandalism by persons or persons unknown. No need to go out on a limb and opine on the possibility that a local 'Squatch didn't like the new temporary camp blocking access to a fishing point or something similar.
All of that being said, it doesn't negate your statement that the Army (most likely the long-term civilian support staff) "knows" that it was a Bigfoot and not a bear, but that report is never get past the relevant commander's desk and is immediately going back for a re-write.