As for why her belongings may have been in the arms room:
If I read correctly, she was supposed to have the day off. Unfortunately, for an armorer, if you are not on official leave or far, far, away from the unit, the arms room must be opened by you or one of the other very few people who have access to the room. I speculate that she was called in to open the vault, which means she will also have to close the vault at some point too. Its not unheard of for an armorer to lock their items inside of the vault if they are taking a quick walk away from it. This could imply that she was fully intending on coming back.
Big question is this: Were the items found inside the armory, behind the spin lock and massive door? Or where the items found before the lock and door? If found behind it, this implies that she locked them inside and fully planned on returning for them, unlocking the vault upon return. If it was found before the big door and lock, then this could possibly indicate she was abducted before opening and unlocking the vault.