Does anybody know anything about, or ever attempted to go to Dettbarn just north of Fauquier?

Looks like it's all yours :)

Ask Stumpy.

So you want to know about Dettbarn do you? I'm one of the few people who can answer your question since I was Stumpy's partner on our infamous Dettbarn trip several years back. You are on the right track about heading in from Fauquier. That's how we did it. It's hilly and dense with brush but it can be done as we discovered. We actually continued on through Dettbarn and followed the creek that leads out of it through a series of small lakes heading east. It was 95 degrees and one of the hardest things I've ever done but it was the adventure of a lifetime. As far as Dettbarn goes it's a beautiful lake and if you go there you would be one of only a few living people to have seen it. Stumpy and I found an old campsite on a back bay with a large built up fire pit complete with a rotted stack of wood. I don't think anyone had been there in decades. At first our imaginations ran wild. We thought someone might have used this spot as a fly in fishing spot with this as their camp back in the days when you could fly into the park. Now our best guess is that the camp was used by trappers or poachers. I say this because there are no fish in Dettbarn. I wouldn't lie about that because if there were and the fishing was great, no one would put the effort into going there; it would just be too much work. I love to fish and I fished Dettbarn up and down and all over. I even brought in my fish finder - nothing. It's a dead lake except for some minnows. Still its over 30 feet deep. So if adventure is what your after, go there. If its fishing stay on Fauquier.

I thought you guys caught a real nice white sucker out der.

What Rangeline said.
One note of caution;
If you decide to exit Dettbarn via the Dettbarn Creek, think it over long & hard. The only parts you can paddle are the lakes & ponds along it. It is a tough, long way through, and once you are a mile or so into it, not easy to retreat.
About halfway through the creek, we opted to bushwhack to the East, camping on a few different lakes before emerging on Turn Lake.
The rest of the info, can be had, at the Bushwhackers Jamboree.

Fauquier itself looks like a good smallmouth lake, also I heard their is some nice lake trout, but I fished it for about a hour and got skunked. Just like Stumpy and Rangeline did I have bushwacked a few lakes and some come up empty, but one lake I went back to, because it just looked too good, and I finally caught a single 2 pound lake trout.

Many little no-name lakes have trout....always fun to find them !

Just thought I'd drag up this old post.