The Standard Massachusetts Auto Insurance Policy contains a coverage exclusion for damages caused where the insured has used alcohol. So, if they paid, their position is that the payment was made in error and they want it back.
See an attorney experienced in insurance coverage issues.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.
The provision in your Standard Massachusetts Automobile Policy where the insurance company can disclaim coverage for being under the influence of alcohol under the Personal Injury Protection portion commonly known as PIP or "no-fault benefits". This portion of the policy pays for reasonable and necessary medical expenses up to certain limits. The Collision portion of your policy under which you recovered for the property damage to your car does not have an exclusion for accidents resulting from being under the influence. It is doubtful that the insurance company could request the check back that they gave you for the damage to the car however, they are probably asking for additional information while they assess whether or not you are entitled to get PIP benefits for your ambulance and hospital treatment and/or any follow-up care who may have received.
Even if your medical bills are not paid by PIP they can still be paid by your health insurance and/or the under the Medical Payments portion of your auto policy.