Ummm...I would send them an email asking why your image was stolen. Yes stolen because they are using it for profit without your permission.

Don't ask for a shirt at this point. Send them a bill for $1500 for a one year useage agreement or ask them to remove it at once with damages paid to you for unauthorized use of an image. If they say you are baseless in your argument then contact a lawyer to draw up a letter and increase the price according to cost of lawyer fees.

Image theft is bullshit and there is no excuse for it in the least. Any company worth a shit would have tracked you down and asked for your permission to use it and made a fair compensation offer.