Ok. Let's start again.
use AppleScript version "2.4"
use framework "Foundation"
use scripting additions
use FMLib : script "fileManagerLib"
set aFileOrPath to "~/Desktop/differentName.rtf"
set folderOrPath to "~/Desktop/testFolder4"
FMLib's copyItem:aFileOrPath uniquelyToFolder:folderOrPath
The file "differentName.rtf" exists on the desktop.
And, on the desktop, there is a folder named "testFolder".
If the folder's name is nor misspelled, there's no error and the file is copied in the folder "testFolder".
But if (like in my script example) the folder's name is misspelled, there's an error saying:
The file "differentName.rtf" does not exists
Where it should be:
The file "testFolder4" does not exists.
In short, the problem is not the term file but the Finder item the error is returning.