That's total bull! If they generally give notice and couldn't because they were busy then that is a problem they will have to deal with. It is not the users issue. At the very least this email should have been your notice, late or not...honnor the orrigional intent which was to give a reasonable warrning!
(Writing the email in a cute and fun tone does not make the company come across easygoing and personable. Content like this is not that easily glossed over.)
