Instructions
Attack the Steal Bot as quickly as possible. If your characters are strong enough, they might be able to eliminate the bot in the battle's first turn. Either way, don't spend your time casting protective spells, as the Steal Bot will get away with one of your items.
Stun the Steal Bot with an EMP Breaker. This item, which can be purchased from a variety of shops in the game, temporarily stuns the bot, rendering it useless and motionless for a few turns. This will allow you plenty of time to eliminate the bot before it can steal one of your items.
Throw bombs and other damaging objects with your healer classes. It may be tempting to just attack like normal with your spell-casters, but throwing bombs and other objects can deal a great amount of damage from a class that typically doesn't deal much damage.