Huh? They lost a guy? Against a small group of bandits?
In that case I have to question why they even bothered attacking those bandits, if there was any risk of casualties. That is just poor math/business if you waste your mercenary company on side-quests like that.
Hell, if they wanted to deal with that situation anyway, they still could have done so safely. Just being well-armed mercenaries on horses could have let them just tell the bandits to scram "or else" (particularly as their presence means the entire company isn't far off). And if they wanted a more final solution to the bandit-problem, they could simply have used the fact that they are on horses to pick them off safely with short-bows, or drive-by spears if they want to be stingy on the arrows.