Muscle regrowth question.?

[socrkeepr29]

So basically I haven't lifted weights consistently for quite some time, but I've recently taken it upon myself to start doing some weightless workouts (focusing on body weight). I don't if it's just me, but I feel like I've already started to regain some size and I've only started doing these workouts a few days ago. I've heard of the term "Muscle Memory", but is it true that your body will regain muscle quickly when you've had it before?