The letter is accurate in its content. Also, it is entirely possible that they did not list INCC as a client in its Annual Report filed with the PCAOB is because the reporting period ends March 31, 2015. INCC may not have been a client until April 1, 2015, which is entirely possible to audit them in that short time period.
In addition, I reread Section 3 of the Exchange Act, and technically INCC does not qualify as an issuer by definition. The firm would not be required pursuant to PCAOB Rules to include INCC in the report. PCAOB requires audit firms to include "issuers".