I know I saw this on another forum, but I can't recall if it was mentioned here....

When Charlie attaches the note to the bird's tag, as he pulls his hand away you can see that he has palmed the note.

So, either he attached no note, or a different note.

Neither Charlie nor Desmond want off the Island and their little discussion before Desmond grabbed the bird was how to deceive Claire so she would stop trying to catch one of the birds and stop this particular plan for rescue from succeeding.