For engineered masonry in essential and nonessential facilities, IBC Sec 2105.2 and MSJC Spec Article 1.4B provide two methods for verifying compliance with f'm. IBC 1708 deals with level of QA and frequency of testing.
The first method dealt with in 2105.2, is the unit strength method and the second method is the prism test method.
In addition to testing masonry units, compliance with f'g is required when the unit strength method is used. The f’g must be equal to f’m but must not be less than 2,000 psi. It seems that the unit strength method is the approach you followed. No?
If compliance with f'm is by the unit strength method, what are the f'm, type of mortar used, and the required net area compressive strength of the CMUs? Do you have test results for compressive strength of the masonry units?
Well, what are the options if compliance with f’m is not achieved with either the UNIT STRENGTH METHOD or the PRISM TEST METHOD? The code (IBC 2105.3) does permit for determining compliance with f'm by testing prisms cut from masonry. If you want to utilize an NDT method as an alternate, it will be prudent to first discuss this approach with the EOR and AHJ/BO in order to seek approval of the NDT method proposed.