Have now read the whole thread and have caught up. The only thing I found on the internet that hasn't been been noted in the thread is a locked up myspace page that Mark had when he was 13 .... his name on this myspace was Hoss 13 and he was advertising himself as much older than 13 (all teens tend to do this so not a biggie).
The other thing that comes to my mind is whether there were any surveillance cameras on any businesses around the area where folks are saying he was walking at 2am. This should be checked to verify that Mark was actually walking to the other friend's house at that time ... if there are any in the area. Also any cameras around the friend's house where he stayed that night.
What businesses are along the route that Mark presumably took after he left his friend's house at 2am. Do we know for sure which route he actually took.
Momtective did some driving around in the area and some of the WSers who are local may know if there are cameras around the route it is believed that Mark took.
What was the weather like at 2am that morning in Lubbock - was it nice and warm, chilly, rainy. Are there any all night pizza places around that area/McDonald's/other fast food places and have they all been questioned.
It is my belief that good old fashioned sleuthing techniques are going to divulge the whereabouts of Mark and I sure hope he is alright and just doing a silly teenage thing.