make a note not accessible

[FlawlessHappiness]

Or you could surround it by an area and make the area have an interact callback. With this callback you could provide a message like: "I should not read this right now"

That won't stop players from reading the note, though. You CAN still pick it up, but to do that, you just need to be inside the script zone that you can interact with. It happened to me.

Not if the note is on a table, and the area is only just covering the note... The player would not be able to get inside the area