Teleporting Demi-cannon

I have an interesting story to relate. I was fighting a battle in my current campaign, I am Russia and was fighting a Swedish army. His army was a few calvary, many line infantry and one demi-cannon. I thought demi-cannon couldn't move, and it was set up well out of range of where I set up my defense. His army advanced and we had a shoot-out where I set up. The battle progressed and he was losing, then out of the blue (as far as I noticed) his demi-cannon was right behind his lines firing on my army. I think it was the demi-cannon because where it was originally it was no more and where it apparently moved to, that cannon had no horsie support. I was wondering if this teleporting artillary thingie has ever happened to anyone else? It was a brilliant battle by the way, he had two stacks to my one. Each of his armies lost 1500-2000 men, I lost about 1600. I'm not saying I'm a terrific player or anything...I play on normal/normal afterall!