A low end worker was shady enough, not the dealership. The last thing a dealership would need is one of their workers to loosen something, cause a major accident, and have the inspectors find something.
Just because these sort of things happen, there's no reason to let them take you.
Keep calm and talk to the manager/ owner. If they ignore or refuse to fix the issue, file a police report, take them to small claims court, and file a statement with the BBB and car manufacturers associated with the dealership. The problem will likely solve itself quickly from there.
The same could easily be said at a restaurant. Mistakes happen and, so long as you're polite and don't cause a commotion, the waiter/ chef would have no reason to mess with anything. If you sense that they had, again, feel free to speak calmly to the manager.
I don't understand the 'it's not worth it' mentality... and I find that that's a big part of what's wrong with society. There's no reason to ever let someone get away with something- especially when the solution is no more difficult than being calm and polite or writing on this forum.