In hindsight, the right move would have been to ask for their phone number and contact information, and tell them you'll get back to them.
If stolen cars are a thing in your area, maybe it's worth renting a garage for the next few months. If they ever broke in and saw the car wasn't there, they probably won't come back.
Also, maybe you can look into a motion detector alarm. Or LoJack? Or The Club? Or all 3 ?
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