I bought it at a Kodak Express shop in SA yesterday.
"Le mieux est l'ennemi du bien." FM Arouet
"All that is necessary for the triumph of evil is for good men to do nothing." Edmund Burke
"Never argue with an idiot. They drag you down to their level, then beat you with experience" Unknown
I just called the shop. They have agreed to replace it.
There is one possible explanation. If your camera's file numbering is set to "continuous" (the default, IIRC), and you put a card in that already has pictures from another Canon on, it will reset the Camera's "current" number to the next one after the sequence on the card, assuming the card has a higher number than the camera's current number.
So for example, I once checked out a 5D demo. Last picture on my card was, say 2000, i.e. this is where my 40D was. The 5D, being a demo, was up to 8000. Put my card in it, took some pics, say up to 8011, then put the card back in the 40D. Now the 40D continued at 8012.
So yeah, if your card had pictures on it, that might explain it.
What Koffie said. Chances are good that the card you put into the camera was used in another camera.
And it doesn't seem to matter which camera brand. I put a card with a Nikon .nef file on it and my Canon picked up the numbering from the .nef file.