So i have to play the whole game,Again to get the pen

((((
Cant i find solution within those red markings u see with special assassin sight?
I dont think The people who created the game would do that so if we miss the pickpocketing thing we have to play the game again....?
I kinda dont like to repeat stuff(especially this,because the game is long)
so if could anyone response give me a tip how to continue with the game bearing in mind i saw the credits stuff(and btw is it long after u escape the building or after u do that it ends?)
Please if anyone could answer.....