Unfortunately the 6900 series phones don't have any visible notification of whether or not the phone is logged into hunt groups. This means that once the message displayed after pressing the HLog softkey disappears, there's no way of telling if your phone will take calls from hunt groups, other than to press HLog again. This is a rather bizarre omission given that queuing on hunt pilots is one of the big new features in CUCM 9.x & that in 9.0 it actually automatically HLogs you out if you don't answer a call from a hunt pilot with queuing enable. Thus it's easy to get into a situation where no one is receiving calls from hunt groups & they have no idea why.
Thankfully in CUCM 9.1 you can disable the auto HLog out of phones via "Automatically Logout Hunt Member on No Answer" within the line group settings. But this still leaves 6900 series phones with no indication of HLog status. The solution is to use a custom phone button template with one of the buttons being the HLog PLK, for example:
The LED on that button then indicates whether or not the phone is logged in to hunt groups. This is actually pretty handy for 7900 series phones too, as their "Logged out of Hunt Group" status message gets overwritten by the number of missed calls status message.