No way to detect a Duplicate Customer Profile?

[fdcyber]

How can I get cybersource createCustomerProfile to detect a duplicate?
I am able to repeatedly send the exact same information, including the following fields:
- buyerInformation.MerchantCustomerID = "1234"
- buyerInformation.Email = "meAgain@cyber.com"
- ClientReferenceInformation.code = "red"
and cyber returns me a new profile id every time (whereas authorize.net would throw a duplicate error if I did this)

Is there any user defined field or fields that cybersource would recognize as unique? (I want to ensure a single customer profile per customer and avoid creating a dup if for some reason the profile is missing from my local cross-reference DB )
Based upon this thread, I guess the answer is probably no Searching CIM Profiles - Cybersource Developer Community

[fdcyber]

thanks, I will be keeping a local cross ref.
If only looking up by buyerInformation.MerchantID would return a record - but it does not.
Look-up-a-customer-Profile-by-buyerInformation 

Are you successfully using the CyberSource API to search for existing profiles?  My lookups by merchantCustomerID return count of zero.