I am not so sure that the risk is that small.
Cyclewise recently suffered. Even if it is nailed down it seems they will have it.
Bike nicked from cycle rack outside Morrisons, staff never used it due to volume of thefts but a customer was not aware of this
Recent posting, last few weeks as I recall, of another bike being taken from roof rack.
Degla seems to suffer more than its fair share of walk/drive offs of bikes.
Yeah you could be lucky and get away with it but how many bikes were found in that poly tunnel in the New Forest recently. Maybe there should be much better/more obvious warning signs at trail centres so as to raise awareness and remind people of the risk.
Edit:
I would add that there have been some good news stories as well where people have been reunited with their trusty steed. Lets hope that this does turn out to be one of these as well. 🙂