Dealing with competence

Me to temp who is entering our zillions of budgets: Did you find any spreadsheets where the electricity account number was wrong?
Temp: Yes I fixed it
Me: Oh, were there a lot of them because if the electricity was wrong it means a lot of other account numbers were wrong too
Temp: There were a few but a fixed them
Me: But there were other accounts that are wrong and you wouldn't have known to fix them, we're going to have to redo them
Temp: No I fixed them
Me: No we changed account numbers midstream you wouldn't have known to fix them because it doesn't affect the calculation

I go off for fifteen minutes looking at the spreadsheets extremely puzzled by why the accounts seem to be correct.

Me: the spreadsheets all seem to be right
Temp: When I noticed the electricity account was wrong I went through every account and changed them to the right ones
Me: Oh. Thank you.

Lesson learned: Occasionally someone does something right.