How did Sprint update you? I don't think there is an automatic way for them to update you unless you took it into the Sprint store to get fixed and they did the upgrade. I think if it was the full Sprint OTA update then yes his HBOOT would have been updated as well. I don't use unrevoked so I am not sure about that, I have always been rooted via Toast since the start. Check this thread though for any options on rooting
http://forum.ppcgeeks.com/htc-evo-4g...roms-wipe.html