You'd have to be stupid and desperate to steal from a garage.

The people who work there aren't office workers; you've got blue collar workers who spend all day working together and hanging out using heavy equipment right in the back. And they're going to be well acquainted with the local tow truck drivers and the local police - so unless you're somewhere like Detroit, you better be on your way across state lines the moment you're out of there. And you're not conning a typical corporate drone who sees 100 faces a day; they'll be able to give a good description.

And then what? You're either stuck filing off VINs and faking a bunch of paperwork, or you have to sell it to a chop shop. The only way it'd plausibly have a decent enough payoff is if you're scouting for unique vehicles with some value (say, a mint condition 3000GT), but that's an even worse proposition for social engineering - people working in a garage are car guys, when someone brings in a cool vehicle everyone's talking about it and the guy who brought it in. Good luck with that :)

Dealership? Even worse proposition, they're actual targets so they know how to track down missing vehicles.

If you really want to steal a car via social engineering, hit a car rental place, give them fake documentation, then drive to a different state to unload it - you still have to fake all the paperwork, and strip anything that identifies it as a rental, and you won't be able to sell to anyone reputable so it'll be a slow process, and you'll need to disguise your appearance differently both times so descriptions don't match later. IOW - if you're doing it right so it has a chance in hell of working, that office job starts to sound a whole lot less tedious.

Way easier to just write code :)