Hello, I'm not sure but I believe that you have to die in the red plane to get some of these notes.

Also, did you get the second note for The Shadow?

can I ask how you finally got the achiev? I am also missing "The Agents".

Right, it's when you first enter the subway, just go to your left.

İlk olarak Zocker96 tarafından gönderildi:

can I ask how you finally got the achiev? I am also missing "The Agents".

That was a year ago, I do not remember well. But I think it was close to a truck. I do not remember what level it was.

İlk olarak edenkun (scorpio)gamehag.com tarafından gönderildi:

Right, it's when you first enter the subway, just go to your left.

Found only one note in the Subway level and I already had it.

İlk olarak FrylockArgento tarafından gönderildi:

İlk olarak Zocker96 tarafından gönderildi:

can I ask how you finally got the achiev? I am also missing "The Agents".

That was a year ago, I do not remember well. But I think it was close to a truck. I do not remember what level it was.

In the last level there is one with a key next to a truck, but I found that one too.

İlk olarak Zocker96 tarafından gönderildi:

İlk olarak FrylockArgento tarafından gönderildi:

That was a year ago, I do not remember well. But I think it was close to a truck. I do not remember what level it was.

In the last level there is one with a key next to a truck, but I found that one too.

then I do not know.

The achievement is bugged. Someone showed me all collectibles and I did found them all.
EDIT: it is not bugged. See the guide.