Trying to track down a airman.?

in 2004 i had a email/penal relationship going with an airman/ historian stationed in afghanistan after he responded to a post i wrte on americasupportsyou.com. we had lost touch by late 2005 and his military email address was no longer active. i have tried a number of times since then to track him down. i just want to make sure he's OK. his sam was sgt. mike sibley. anyone know how i can track him down?