I never ever consider leaving my car keys in the caravan at any time while we are out and about. If someone did access the caravan and pinch the keys, will the insurance pay out as a caravan may not be considered as a safe place.
if we were 600 miles away, we have two options. One would be to phone the daughter and ask her to arrange a courier for the keys or contact the nearest dealership and buy a replacement set.
Just to add, in the past we have had two cars stolen at different times and now I am a bit paranoid about security.