Get-User with userproxyfull object

Seasons Greetings everyone. I have the following code that finds the membership of a user object in AD LDS without problems
get-aduser -Server localhost:50000 -Identity “CN=Rob Armitage,OU=myOrg,DC=d1,DC=ms,DC=mycompany,DC=com” `
-partition “DC=d1,DC=ms,DC=mycompany,DC=com” -properties memberof |Where-Object {$_.memberOf -like “cn=the*”}

However if the identity is a userproxyfull object it fails complaining that it cannot find the object.

Many thanks

Update. My code seems to work with the same syntax but using get-adobject instead.