What is that saying?

What is that saying, "While the cat is away, the mice will play." Is that the correct saying? I have issues with getting saying mixed up....Anyway, this is an email I received today from one of my employees:

I am writing in regard to a certain person’s work habits, because I feel it is adversely affecting the work environment here. XXXXX’s work breaks are getting outrageous. It’s not that I want you to come down hard on her/him or anything, but it’s affecting the work place. XYZ customer called for XXXXX at least three times today. Twice while XXXXX was on a close to hour-and-a-half lunch break and once while XXXXX was in the bathroom. I think XXXXX does a great job here, and she/he is very generous to us all, picking up food for us (for example). She does his/her share while he/she is here, but it’s getting to be hard with him/her gone so much. Can you please gently let XXXXX know that it would help us all if he/she wasn’t gone so often for so long? It’s not like he/she eats his/her lunch on the hour that he/she is gone to pick up his/her daughter and takes a fifteen minute break in the morning. He/She was gone almost a total of 2 ½ hours today. It’s just frustrating to me, but maybe I’m over-reacting.

I know XXXXX has some long days here, so I do recognize that his/her breaks should exceed some others. For instance, my breaks don’t need to exceed 30 min, because I’m only here maybe 7hrs a day on average. In short, he/she has a right to more or longer breaks, but two hour-and-fifteen min breaks seems like a lot. Plus, we all have to schedule our breaks around his/her two breaks.

Sorry if this is annoying you on your sick time off. I just felt I should address the issue since it is bothering me so much.