Yes I am in the latest OS and firmware saw it on settings also I can tell because I see the double tap to wake and hp financial calculator but on my app list I don't have hp display tools.
That's really strange... does the app launch when you connect an external display?
The app does not seem to be listed on the Windows Store, so I am not sure how you could get it other than a firmware update or using WDRT (Windows Device Recovery Tool) to reload the device with the latest firmware. You can try WDRT if you really want the app now, but this will reset the device and you will have to restore your apps and settings from a backup. Otherwise, it might show up after the next firmware update, but you'll have to wait for that (shouldn't be extremely long wait though, probably no longer than a month).