I took a look at this one again.
The "Treasure Seeker" and "Treasure Hunter" tasks are fully implemented, and have been since Build 30000.
Sounds like the issue may have been you had extra tokens in your prefs.cs file from other accounts (or offline play), and you were comparing your Statistics tab (which is based on prefs, not the server) to verify whether or not you should be able to complete the task, when in reality, the server had your account logged with less tokens than what was required to claim the task reward.
I adjusted some client side and server side code to make the token count work properly. I've added a field to the "Statistics - Overview" panel which will show you the total number of tokens collected according to the server to make it easier to track your progress towards this line of achievements.
I'll revamp the Completion statistics at some point down the road to pull data from the server rather than the local client prefs. I'll post again if and when this gets revamped.
~Aayrl