Lost - This is an Ear Training exercise. It is not even about playing the piano. It is not about watching someone play it, and remembering the visual. It is about developing the ear to be able to reproduce what it just heard. This exercise - in a broader sense - has to do with developing as a musician.
This can be a very useful tool for arranging parts on the fly, without the aid of a piano. It is also useful for improvisation and, most significantly. composing.
Ranjit.
This exercise is akin to the children's game 'Operator' - where a message is whispered from one to another, and the humor of how that message is distorted - as it is passed on.
The main thing here is using your voice.
You don't have to do solfeg - as such. You just need to be able to sing the scale in relation to the key signature. Usually the tonic is struck first - to acclimatize the ear to the proper scale.
The ear muscle may not grasp 4 bars on first listening. Perhaps you can start smaller, by at first trying to sing back 1 bar after one listening. Then, try an exercise with 2 bars. etc.
The rhythmic dictation described in the video is a tool I use for students, and is very effective.
So, try smaller segments, and work up from there. You can practice singing bits anywhere, practically, like in the car, listening to the radio. Let it play a few second or so, turn down the radio, and repeat it with your voice. The more you use that muscle, the stronger it gets.
Music, in its most essential experience is about listening. Seeing it, watching it, is secondary.