My physicians will prescribe an alternate if their first choice is not on the formulary. Did you bother to check the formulary yourself to see if there was an error in determining coverage? Also, as I recall, the cost of this med is not that great; you cost to file for contempt for this one item is likely to be more than simply paying for the drug yourself. Wait until it is cost effective to file. If this is a consistent problem, the two of you should compare health care options available to each of you; it may be beneficial to revisit which parent provides the insurance coverage or the plan choice.
BTW, you do not earn brownie points with other parent by referring to the child as "my" rather than "our" child. You are the one who wanted to make a "point" out of the problem. You can certainly file for contempt and create conflict rather than agreeing next time to check the formulary before committing the other parent to uncovered drug costs.

