An employer is prohibited from asking your age in a job interview. Also, age should not be a factor in an employer's post-hiring employment decisions. But, you have no viable legal claim until you suffer an adverse employment decision based arguably on age. You should document, off the clock and off the premises, the conversation you had with the owner as to date, time, place, witnesses if any, and the words said so you may use that document to refresh your recollection if needed in the future. Continue to do your job as best you can and to follow all company policies. Don't give the employer any independent, so-called "legitimate" reason to chose a younger person over you in a reduction-in-workforce. Be alert for any other age-biased comments by the owner or management, and if they occur, document those also.
Document the incident. If you suffer an adverse employment action, this will help you circumstantially. As of now there has been no violation of the law unless OH has laws against it. Maybe check with a local employment attorney.