When fight is finished, temp item will be re-equiped by default if used (and you have another one in tour inventory), unless you set if to 'off' in preferences.
Reequipped, but should be 1 item less in the inventory. I didn't register any loss of items after fight. If this problem remains, I'd have unlimited chances of using temp weapons.
Seems the problem is with the inventory. It says the incorrect number. But when I go to shop or on my faction's armory donation page, I get the correct value - they say its 2 bricks, which means 1 equipped which means 1 used.