Is it possible to look up a customer profile using buyerInformation.MerchantCustomerID?

I can do a search but my one and only customer in test is not found (count = 0)

The docs here Filtering by Query Parameter (cybersource.com) say buyerInformation.MerchantCustomerID is a valid query term.
But is this search only for transactions?  Am I still stuck with having no way to find a profile using a MerchantCustomerID?
Authorize.net docs say to try to create it and get the duplicate key error OR fetch them all and search locally ( I  would rather not fetch 200k+ records to see if cyber has a profile that I don't.)
So is there still no way to search for a customer profile with the API except by using  cybersource profile ID?