Goathair,
In a later post, you confirmed he was a sniper.
Weapons Company, 2nd Battalion, 25th Marines has a sniper unit based in Garden City. Probably the only reserve outfit on Long Island with such a unit, so I assume this is the one. Being that the 2/25's Services Company is also located at Garden City, I'd venture to guess that a sniper could pretty much get their hands on all the burlap they ever wanted.
As you suggested, the dates would match up pretty well.
Dates that GB4 went missing:
1) July 9, 2007
2) July 10, 2009
3) June 6, 2010
4) September 2, 2010
Dates of 2/25 Deployment in Iraq:
From:
http://www.marines.mil/unit/marforres/4thMarDiv/25thMar/2ndBn/Pages/UnitHistory.aspx
"In September 2008, 2/25, with individual augments from 1/25 and 3/25, deployed to Al Anbar Province in support of Operation Iraqi Freedom. The battalion was split in two 500 marine "half-battalion" units to pursue separate missions: Force protection of Al Asad Air Base and counter insurgency operations in the area around Camp Korean Village, Iraq. 2/25 Demobilized and returned to Garden City, New York on 10 April 2009, after turning over the security of Al Asad Air Base to 1st Battalion 8th Marines. In the Summer of 2010, over 400 Marines from 2/25 deployed to Mozambique to train with the local military, and conduct humanitarian medical Civil Affairs in towns near the capital."
http://www.wikihow.com/Make-a-Military-Style-Ghillie-Suit
https://secure.wikimedia.org/wikipedia/en/wiki/2nd_Battalion_25th_Marines
http://www.marines.mil/unit/marforres/4thMarDiv/25thMar/Pages/default.aspx