Being dismembered from two arms to one (in this case, by a snapjaw skullsplitter, and previously, a madpole,) removes the arm and hand slot for that arm. It also unequips any missile weapon in the respective slot, but doesn't seem to remove the missile slot.

This means that it's possible to just re-equip any missile weapon to the slot again, and go on as if nothing had happened, including two-handed missile weapons like rifles or bows.

ex: if you have left/right arms, hands, and missile weapons and get the left arm dismembered, you'll now have the slots for right arm, right hand, and both left/right missile weapon slots still usable.