I didn't ask prior to purchase because House sent me this on the 27th February, where I bought the script on the 6th march (my birthday!). The script was first discussed on the 27th February; where I agreed I'd buy it and we would do the deal when he had done the script + back from holiday etc; ensuring every "every script I sell to a customer is unique by code so that's not a worry". This lead me to believe it wasn't necessary to ask it was private.
Proof of it being 'unique by code' on 27th February:
Proof of payment on 6th march: