Only three main roads is actually a good thing. Now I would assume there are all kinds of side roads, dirt driveways and trails. For those in the area, here are some things to consider. First, do the individuals you consider POI's have or have access to ATV's? Second, what you are looking for are dirt roads, trails and fire trails that a person can carry someone down on foot or on an ATV. On foot they are not going to go very far and not very far off the trail (people are heavy), or excavate a very deep hole. On an ATV, they will go a bit further, but not over downed trees etc. Again, not far off the trail or very deep. There may be animal activity as horrible as that sounds...
On your forays onto the mountain, keep an eye out for anyone who owns an excavator or backhoe AND is friends with the POI's OR can be bought for the right price. Just keep that information in your notes should it become important later and you can hand a nice little list over to LE to save them time.
Keep one thing in mind..you are putting yourself in harms way. Do not go poking around on your own...make sure there are at least four of you. As has been noted here before, we are all only one bad decision away from being a subject of discussion in this forum.
James went missing on my Birthday. 
