The term "Muscle memory" has in correctly coined by regular gym users over the years. Many believe that after a period of non-training where muscle loss occurs (Eg taking a few months off from weight training), after returning back to weight training your muscle will regain strength and size quickly because of "muscle memory". This is not true.
Muscle memory is actually about neural patterns and efficiency of movement. It's a form of motor learning. It involves consolidation of a specific movement through repetition so the task becomes automatic. For example we practice walking all the time, we don't think about how to walk- we just do it. This allows the brain to be able to think of other useful things whilst walking, like dodging out of the way of incoming traffic!
So if you have had a long period of time off from training unfortunately this doesn't mean your going to gain muscle quicker than a newbie weight lifter.
Muscle takes the same amount of time of breakdown and repair in every body. So its time, intensity, genetics and volume of training that will impact how quickly you grow muscle.
The only advantage an experienced detrained weight lifter will have over a novice will be that motor patterns in lifting sequence will already be there.
This means you don't need to spend time learning new motor patterns "new things". This give you a time advantage in that you'll be able to get straight into lifting were as a novice will have to learn how to lift first.