Blog Hi-jacking

My blog was temporarily hi-jacked today. They hacked into my template and pasted it all over with a frog advertising some website. You couldn't even read a word! I deleted big portions of my template and this was as close as I could get to normal. I lost my light blue background and could not get it back, but at least the obnoxious amphibian is gone. Scary that people can do that. Got no help from blogger either about how to fix the problem. Ugh!