After 24hrs you can rewrite gone with the wind as a bump if you feel like it.
Bumping to mark sold serves no purpose. It takes it to the top so folks go look and see if the price is reduced, etc.
Just edit the original post to mark it sold and close the thread, that will not "bump" it to the top.
If it has been 24 hours and you want to bump it to the top because it is still for sale (the purpose of "bumping" an ad), then type whatever you want in a new post.
A new post to mark it sold serves no purpose and pushes everyone else's ad down for no reason.
I made it 750 for stored messages for site supporters, try that