I'm over near Seattle, but some things worry me about this case.
I found a map which shows where he went missing:
http://www.mibsar.com/Cases/Gray/SkyValleyChronicleMap.jpg
It's been a long time since I drove on Sol Duc Hot Spring Road but it's very rural, and even the area around it is a park with very little in the way of services. The road itself is there to get to the hot springs and a few campgrounds. The resort was open this year when he went missing, so if he made it back to the road he should have been spotted. The road is closed during winter, as is the resort (in fact it is already closed this year.)
The nearest proper towns would be either Port Angeles or Forks, either of which is about 20 miles away as the crow flies - but there are plenty of mountains in the way. Route 101 (which is the main loop through Olympic National Park) is heavily traveled once it opens so if he somehow made it there (about 2 miles as the crow flies) he would have been seen pretty quickly.
Also looking at the NPS maps (
https://www.nps.gov/olym/planyourvisit/upload/wildernessmap-10-25-16.pdf) there's really nothing around where Jacob went missing except for the trail.
So let's look at the Aurora Ridge Trail, since his belongings were found at the trailhead.
The Washington Trails Association has people discussing this trail - there's some good insight here (
AllTrails has some information as well.) It's advertised as having moderate traffic, but there aren't many reviews of this trail leading me to think that this is actually not a high traffic trail, and it doesn't get as much maintenance as a result. It sounds like a difficult trail, with a number of ways to get lost (game trails and such) - over 9K elevation gain for a 30 mile hike is challenging. Some also mention the trail is steep (could Jacob have fallen?) and that there are some aggressive goats on the trail. There's also limited water.
We don't know what kind of shape Jacob was in (I'm guessing good because he was trying to bike from Washington to Vermont), so he may have been in good enough shape to get far on the trail but perhaps gotten lost or injured; he may even have not brought enough water with him and had to go off-trail. With the description of the trail, it sounds like it could have been very difficult for SAR to be able to find him if he had fallen or wandered off the trail for water. The dogs picked up a scent but he could be anywhere if he had (for instance) decided to try to follow a source of water down instead of going back on the trail.