Finding not used extensionAttributes

Hi there,

anyone has a clue why the first PS command doesn´t return any extensionAttributes (in my example eA1) while the other one does. The point is that I need to find two extensionAttributes that are not in use by thousends of users.

Get-ADUser -Filter * -SearchBase "DC=emea,DC=zf-world,DC=com" -Properties extensionAttribute1 | Export-CSV -path d:\scripts\pwd-lastset\CustomAttr.csv (this one fails)

Get-ADUser -Filter {extensionAttribute1 -like "*"} -SearchBase "DC=emea,DC=zf-world,DC=com" -Properties extensionAttribute1 | Export-CSV -path d:\scripts\pwd-lastset\CustomAttr.csv