Is there a way to get an accurate timestamp associated with recorded audio samples?
Similar to pu64QPCPosition that is available with IAudioCaptureClient::GetBuffer
No, FMOD does not store the platform dependent timing information.
For general background, during each pass of the FMOD mixer all recorded audio since the last pass is copied to the specified FMOD::Sound, you can track the write position within the sound by calling System::getRecordPosition.