Well, with all those Beautiful cars & interiors, if you have an elec. fuel pump, hide a power switch or pull the fuse.
For a manual fuel pump, hide a shut-off valve.
What about a removable steering wheel-- steel plate covers the coloum & can not be removed without the key theat unlocks it?
As stated earlier, you can make it difficult enough for them to give up.
It's Your Secret, keep it that way!!