So, here's my analysis. The car-by-boatramp seems 100%. So..
1) He had a secondary vehicle parked there or used a basic watercraft to reach a secondary vehicle. Upstream is the scene and there is a dam just downstream, but brief use of water would throw off the dogs regardless. He hasn't been found in over 3 hours x 75 mph on the highway means he is somewhere in here:
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If this is the case, he may not turn up for weeks, months or even years. His cash will run out so unless he has a stolen identity to operate under, so he'll be found eventually. Whether or not an accomplice picked him up doesn't change much, and I can't fathom he had a "buddy helping the cause", just no way...
2) You bet your ass that chopper had FLIR as well. If he proceeded on foot with a half-hour head start, and likely being in shape, he was 2 miles away by the time they got there and probably 6 miles away long before a good scent would have been found. Seems if he was on foot exclusively, they'd have found him by now either by flir or dogs. Regardless, as of midnight, if he was on foot, he's somewhere in here:
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That's a lot of square miles and thousands of hiding places given all the unoccupied vacation homes, cabins, general abandoned buildings, etc... Even a Watertownesque response won't produce him for days. At some point his food/water stash will run out if he even has one, and no way he'd make it into public locally without being spotted. He'll either get caught foraging or B&E, but his could be upwards of 1-3 weeks if he planned ahead.