Was your car ever found? I investigate insurance claims, and you cannot give a definitive ''it can't be stolen withou a key'' answer - it's not true. if a car never turns up, it is very plausible it was towed away - as mentioned.
However, there were a series of thefts about three years ago in the lake District where a load of Freelanders were stolen without the keys from campsites. The police told me they knew they were taken and driven without the keys, but the few people they caught wouldn't tell them how.
What insurance company was it who refused to pay (hope it wasn't me!)