Take a deep breathe and do not panic. It probably was not stolen. The federal government requires them to send you a letter if, say, your check went to the wrong address because you have the same name as some other policyholder. Also, if it was serious, they may be required to pay for credit monitoring for a year. (So you can call and ask if they are providing that.) If it wasn't that serious, you probably have nothing to worry about.

I used to process insurance claims for a living. I have written a few letters informing customers of a privacy breach. The vast majority of the time, the customer really had nothing to worry about. Most customers who get a check or letter that wasn't intended for them are not career criminals waiting with baited breathe to get your info. In fact, I have had to write privacy breach letters when we sent the info to the guy's father by the same name or mother whom they still lived with (or twin brother with a near identical name). Federal law compels the insurance company to inform you. But unless you see weird charges or something, you probably have nothing to be worried about.

Generally when this happens, the company which had the breach will provide free credit monitoring service to the affected customers. You should ask them about that. If they're not doing it yet, you should. Chances are nothing will happen, but if someone does use your social security number to sign up for a credit card, loan or other service that impacts your credit rating, a credit monitoring service would notify you of that.

Thanks - yes, the insurance company did offer a free year of this service. I will be signing up for it.

Contact the major credit bureaus and request they put you on fraud alert