I have not thru-hiked (yet). However, I have been "clean" and in recovery for over 25 years. I am a pastor and military chaplain. I am also a certified alcohol and other drug counselor. Here are some tips that I would share for 12 Steppers:
Look for 12 step groups that meet in towns that are near the trail. Make contact with people from those groups PRIOR to your hike--and carry the contact information with you. Call these people again as you near those towns and request a ride to the meeting. I am pretty certain that SOMEONE would be more than happy to meet you and give you a ride.
Here are some starter websites to help you find meetings. If you need information for other types of 12 Step groups (or more information about the groups listed below) please send me a PM (Private Message) and I will try to help.
For Alcoholics Anonymous:
http://www.aa.org/lang/en/meeting_fi...fm?origpage=29
http://www.step12.com/meetings.html
For Narcotics Anonymous:
http://portaltools.na.org/portaltools/MeetingLoc/
For Gambler's Anonymous:
http://www.gamblersanonymous.org/mtgdirTOP.html
If you are an alcoholic--and there is no AA meeting in the area where you are hiking --my guess is that folks at MOST NA or GA meetings would welcome you with open arms--especially if you explained your situation. However, you might want to check with the group in advance just to make certain. SOME groups are not as willing as others to open their meetings to folks with another types of addiction.
I would carry 12 step literature with me on my hike--possibly daily devotional type of 12 step literature. I would not only carry it--I would also READ IT!
I would carry a cell phone--and a sponsor's contact number. The phone could also be used to help you phone for rides to meetings.
You could use public computers at libraries and other public places near the trail to contact online 12 step meetings and forums. You could also carry a Blackberry, iPhone or similar web-capable device to access online meetings. Some of the many sites include:
http://www.12stepforums.net/aagroup.html
http://www.recoveryrealm.com/
Keep your eyes and ears open on the trail for other possible 12 Steppers. Even in the midst of the Hurricane Katrina disaster response I bumped into other 12 Step folks and we held our own informal "generic" 12 step meetings in the middle of a totally destroyed New Orleans. Some "meetings" were as simple as just two of us recovering folks talking to each other about our addiction and our recovery (like Doctor Bob and Bill W. did in the earliest days of the program). We had other informal "meetings" that had more structure--such as reading the 12 steps/12 traditions, Serenity Prayer, reading from a "Big Book", etc. Having informal "partial" meetings is better than attending no meetings at all (and sometimes such informal meetings are even better than formal meetings!!!!)
Anyone with recovery issues please feel free to PM me to brainstorm other possible ideas and solutions. (and if I have questions, I will try to find you and contact you!)