That's incorrect information.
A thread can only be "locked" by the moderators. Locking a thread prevents any further posting within the thread.
From the FAQ: "Users can edit their own posts up to 4320 minutes after they are made." That's 3 days in normalspeak.
If 3 days have past, rather than start yet another thread with books that haven't sold, you still still post in the thread, you just can't change posts older than 3 days. You can add to the thread by saying something akin to "The following books are still available..."
Flaming Telepath has managed many successful sales threads using this methodology.
Over easy or scrambled?
(thumbs u