cyphix, thanks for your EXCELLENT question!
Here is the answer: As a very valuable add-on, giving members the ability to "stick" threads was indeed added, but because of the sensitive nature of this, it is limited to the "Domains for Sale" forum only.
The rewards store information was updated to reflect this, and there is much gratitude to you for helping to uncover the incomplete description of this feature in the rewards store.
As usual, your contribution is always high quality, and much appreciated!
If you have any further questions, give me a shout!
WebCat