Have you also had something like a check engine or service engine light? There's got to be some information missing here. VSC is the vehicle stability control. There is nothing whatsoever in that system that is in any way relevant to gas caps and air hoses. So - the mechanic put it on a computer and did find some kind of error codes. You just need to find out what they are. They look like "P1234." You could have been told that no code shows that is relevant to the VSC system. You also cannot get the computer to tell you what the fix is. The computer just provides data. It remains for a human to actually figure out what is going on.
So if you want some help with it give the mechanic a call or check your invoice for more details. In particular, any error codes that were present in the computer. If your check engine light is on then many auto parts stores will read your error codes for free. Once again, they look like "P1234" and folks here would need to know the exact code.
If you trust your mechanic why not have him/her take another look? In general its almost never the case that you have to go to a dealer - warranty & recall services are about it.