This has nothing to do with Hi5 players. The player who went for your bounty would have been under the 30 day protection rule where they can not be punched by higher levels, even if they went for your bounty.
All new players get 30 days of protection, except on Zombie Slayer, where they get 7. It has nothing to do with Hi5 players at all. All new players get the protection. What makes you think it would only be given to Hi5 players?