Some one has bumped it . There are two kinds of bumps. 1. Mini bump 2. Super bump
For mini bump you must make posts.
For super bump you only need to click on "Bump" button.
A high-merit user has likely clicked on the button. ( Maybe more than 1 user)
As the bump power decreases by time and becomes zero after 36 hours, such topics cannot remain on the top.
Some one has misused the bumping points or some one has tested it.
Thank you for the explanation. I still need clarification on something please, if I may....
From what I can see the way this is set-up is open to a different type of abuse, a kind of
out of the frying pan and in to the fire type of situation because the bump-power can be purchased as well as mini-bumping still going on directly from posting.
This new strategy does not exactly fill me with confidence - unless I am missing something from the OP