Are you using Aruba air monitors and APs? Or are your switches reporting up to RAPIDS?
Note that while hidden SSIDs can take longer to discover (unless clients are active on the SSID then detection is just as quick), they can still be detected, hidden or not, since the actual 'hiding' of the SSID doesn't really prevent the probe-requests and responses from happening, and once that occurs, assuming you have AMs and/or switches reporting up to RAPIDS/AirWave, they will be detected, and certainly once a client associates. It's a regular test we do with our Federal customers.