Just a little follow up on this forum post. We found and used the following stackoverflow question and used the javascript code to pop up a message to the user when they are running in private mode in Safari.
http://stackoverflow.com/questions/2860879/detecting-if-a-browser-is-using-private-browsing-mode
try { // try to use localStorage localStorage.test = 2; } catch (e) { // there was an error so... alert('You are in Privacy Mode\nPlease deactivate Privacy Mode and then reload the page.'); }