what would you do?

[TimF]

Came out 1hr later & my bike had been moved.
The steering lock was on & so they just pushed it around in a curve. It was now across & totally blocking the concrete footpath.

There seems to be a serious breakdown or misunderstanding in etiquette here. We're not talking about a BMX bike... I mean, can you imagine if someone did the same thing to a car? "I'll just jump in, pop it in neutral, and roll it over there." Everyone would understand that it is unacceptable, that you can't just muck around with a strangers vehicle.