I have seen this type of references in other threads too where the service center later claims the work was done but they forgot to put it in the papers. If they didn't document it how can they go back and verify the work? They must be working on multiple cars a day. No way to really know. We have no choice but to trust them.
One thing is that there is only a standard set of repairs that they can use. For example, I had a problem with the lights being adjusted too low, but the only thing they could put in was that the lights were adjusted too high. This is somewhat worrying because a new car can have problems that weren't thought of when making the list.