On occasion I look at my watch and write notes like I am a mystery shopper just to see if the service improves. I mentioned this previously and a member of the forum said it makes it harder for the shoppers.
This is a teaching moment. In my opinion, the servers and associates know they are being shopped. You should use a Digital recorder and not take a written note. When you get home you can debrief the recorder and get all the info.
I just tell the partner I am dining with the visual snapshot I am taking and the recorder is recording the mark that I drop or the server drops to mark the time and events that are occurring.
If I am shopping alone I talk to myself. People do that all the time. Before the age of cell phones, they would have dropped a net on you if you talked to yourself. You must be discrete when you talk to yourself.
If you are a professional you can be sneaky and get all that info, even if you have to say "WOW", OMG, Yikes, grunt or groan or make other exclamations and remember what was happening when you marked that time. You can tell the recorder what happened when you grunted or groaned as soon as you do not have associates watching you or within earshot.
Practice before you go for real so you know what your recorder can hear. Be aware of music that might be playing or crowd noise in restaurants.