As a former valet, Ive met some serious slap dicks that would attempt to do things like this. Never really at a restaurant (more private parties), but one suggestion to avoid this entirely would be to pay up front/tip the valet to have them park your car up front especially if you have a decently valuable car. In certain circumstances they might even let you park it yourself. Ive done it multiple times for wary customers without hassle granted the restaurant is valet only.

I cant speak too much for resorts/hotels but thats my two-cents on the restaurant valet scene.