It doesn't sound like you missed anything..... regardless of what the gas company says. The repair sounds like it will be totally inexpensive. Everyone just gets upset about the 'what if' scenarios, especially when it comes to things like gas leaks.

I know it's tough to not step back and re-think how you inspect. In reality, a lot of call backs are very random things and you can't possibly forsee the next one. Just chalk it up to experience and add it to your list of things to be aware of.