OK, detection method was "not blank" (returned $False) instead of doing nothing in the script block.
detection method
$targetpath = [Environment]::GetFolderPath("CommonDesktopDirectory")
$shortcut_location = $targetpath + "\Facebook.lnk"
if (test-path -PathType Leaf $shortcut_location ) {
Write-Output $true
}
else {
# Write-Output $false
}
detection method
Will leave here in case it helps someone else. :)