How can the MSC ask me for more information after my report was already submitted, approved and good to go? Why is their mistake my problem?
Don't get me wrong, I didn't do those things hoping to get something out of it. I try to be helpful because it's good business.
I think you are looking at this from an employee/employer standpoint instead of supplier/client.
You're Lowes, you're not the employee.
Keep your client happy, help them out when you can, they'll come back and buy more mowers from you.
When I have a bookkeeping client who asks me to do extra, I happily comply, but I also charge them for the time it took me to do their extra work. I don't do more work for the same amount of money, and my client doesn't expect me to.
To me the issue is twofold with the elapsed time being the minor of the two. Regardless of how much time has passed, I do my best to provide additional information. In the OP's case the questions asked were not part of the scope of the original assignment. Even with copious notes the OP may not have the answers.