Credit for flight on other side of world...

Dear sages,

I write this not as a "Cool, I got free miles."

Rather, I write trying to figure out how it happened.

I received credit today for a flight ZRH-VIE on LX. I didn't take the flight, nor do I believe was I ever ticketed for this flight. I've looked through my records to see if at some point I purchased a ticket for this route. But I can find it.

So, did someone who flew the route not get the credit because it somehow came to me? Is it possible that I did have a ticket for this flight and it was credited even though I cancelled it long ago?

I plan to call MP and have them remove the credit. It's just kind of weird.