Brent Johns Tree Frog Media Paid to have a website designed - used unlicensed images and now we are being sued Kuna Idaho

We hired Brent Johns of Tree Frog Media to design a website for us.  Website was of satisfactory quality and arrived a little behind schedual and a little over budger - but that was ok by us.  1 year later we receive a notice from a stock internet photo company that the images on our website are copyrighted and he did not have a license to use them.  They are asking for a 4 digit settlement and we are ultimately responsible as the end user since we cannot get Brent to contact us back.  From what others have said - this kind of situation is not that uncommon.