historian, methinks you're confusing fact with fiction.
Reality with fantasy.
Since you've not provided any evidence to support your claims of invisible bigfoot, I counterclaim that what you're describing is the dreaded mudwumple* and not a bigfoot at all.
RayG
* mudwumple = an undiscovered, unclassified, legendary creature that supposedly looks a lot like a very large alligator/crocodile, but with very long legs (so much so that they can run bipedally at very high speed for short distances), oddly shaped feet, and they are reportedly much bigger, smarter, stronger and faster than a regular alligator or crocodile. Mudwumples are sometimes described as large, scaly bipedal reptilians, and many believe that this animal, or its close relatives, may be found around the world under different regional names, such as the Google of Tibet and Nepal, the Yahoo of mainland China, and the Yipee of Australia.
Mudwumple supporters fall into two main camps -- those that believe it's a flesh and blood creature, and those who believe it's paranormal (communicate telepathically, pilot UFOs, have mastered the art of invisibility, and control alternate dimensions.) Science seems to take neither side seriously.
Mudwumples are mentioned in many Native legends which tell tales of them carrying off young children, killing, and eating them. No bones, or bodyparts of the mudwumple have ever been found, but mudwumple supporters point to a film shot by an intrepid mudwumple enthusiast 40 years ago as evidence of the creature. Though much controversy exists today over this unique film, no one has ever proven it to be real or hoaxed. Some individuals have come forward claiming to be the wearer of the mudwumple suit shown in the film, but no suit or costume has ever been produced. Detailed analysis of the film seems to show a creature with inhuman characteristics and features. (its legs are too long, arms too short, shoulders too narrow, and head to large for it to have been a person in a suit. It walks with a rather peculiar bow-legged/knock-kneed gait as well.)
Tracks and other mudwumple evidence have been found, and some point to DNA tests on scales and toenails recovered near mudwumple sightings that have come back as 'unidentified reptile' as evidence of mudwumples. Many books have been written about mudwumples, though precious few articles appear in scientific journals, and only a few open-minded scientists think the evidence is compelling enough to warrant further investigation.
Many mudwumple organizations, websites, and message forums have sprung up across the world, but there is sometimes much disagreement between them. One well known organization, calling itself "The scientific research organization exploring the mudwumple mystery", conducts expeditions to raise money for further mudwumple research.
Some scoftics/skeptics claim that mudwumple evidence has been hoaxed, but they have not been able to reproduce any realistic copies of tracks or suits, so their arguments can be ignored.