There is apparently a script at Gori where guerillas that go with you on scouting missions take their equipment from the inventory. The equipment include:
Mk18 + DMS for the marksman
Mk200 for the autorifleman
TRG-20 and RPG-42 for the AT rifleman

Problem is, whenever the map refreshes, i.e. if you restart or attend a briefing, the script runs again and the inventory of all the equipment above goes down by another unit. Eventually your inventory for these items will disappear completely as you progress through the campaign.