I had this happen too - after the mission where you rescue the winged demon-y person from the bandit vault. Mission was successful, no losses on my side.
My lancer person's lance and my bandit's axes all disappeared, replaced with swords that they couldn't use, and a bunch of leather armor, and many other characters' inventories were randomly swapped around. Since it makes two key melee characters essentially worthless for the next several missions (until you see a merchant again) this is pretty nearly a game-over bug.
My lancer person's lance and my bandit's axes all disappeared, replaced with swords that they couldn't use, and a bunch of leather armor, and many other characters' inventories were randomly swapped around. Since it makes two key melee characters essentially worthless for the next several missions (until you see a merchant again) this is pretty nearly a game-over bug.