What is the ruling on saying the phrase "ya batil" (oh falsehood/vain) if it is used for expressing astonishment or discomfort, and is not intended as a plea for help or a direct address?

If the situation is as described, then such a phrase has no relation to the forbidden seeking of aid from other than Allah. The metaphorical calling upon things is not part of polytheistic seeking of aid, and there is no harm in applying this phrase to that which is false.