Click -> Story or Video
The symptoms sound like a concussion. "Words slurred, disoriented..."
He was only going 18 miles that day and from the map it looks like only half of the trip was in the woods and the return on roads.
This is a classic case of underestimating the power of cold weather when you are immobilized from an injury.
This could have easily happened in our forest.
Mountain Biking is dangerous!
1) Please don't ride alone if you can avoid it.
2) Use an app that maps your ride and provides regular links to loved ones so they know you are OK. I use Cycle Meter.
3) Provide the cell phone numbers of other mountain bikers to your family. Tell them to inform other riders of the situation as soon as possible. Large numbers of people familiar with the area and physically capable of performing a timely search will increase the opportunity to successfully find and extract the victim quickly. The more the merrier!
4) Always leave a note with the time you plan to hit the trail and where you plan to go.
Be careful out there.