How quick can you lose muscle if you don't work out?

SAC0O3

I have been doing barre pilates for over a month now three times a week. I have gotten a great core and muscles BUT this past week has just been packed and I couldn't go. (They only have the class once a day three times a week and I missed them all due to random things) There is no excuse why I have not done any exercise at home but I have not done any squats or lifted any weights. Am I going to lose my muscles already? I probably wont work out again until Monday and then I will be back on schedule.