Honestly, I think it's best that you drop it and walk away from the situation. With him being in the military now, you will have a pretty difficult time contacting him especially with the way his mother is acting.
You were naive and believed a "best friend" so take this as a lesson learned and drop the situation.
$3500 is a lot of money to lose to someone so underserving but you can ALWAYS make another $3500. However, the time you spend and waste on inconsiderate, immature and unappreciating people, you will NEVER get back.
As frustrating as the situation is, your time is more valuable and important than the money/items you lost. Save yourself the trouble and move on and who cares if he doesn't contact you. He doesn't deserve you as a friend anyways.
Let karma hit him for you. =)