Shizam

Oh, that makes sense. There's a pretty high chance that a generic item will spawn in barn and one of those items is a matchbox. Offices still have the best chance though. http://picacid.com/arma2/loot_en.html that's the loot list if you want to see it.

According to the loots list you can find them in residential areas, offices, and churches all at the same rate. They're not terribly rare, but it's not hard to understand having some difficulty finding them.