Luckily, they've placed it back to their product listings. I thought I'm going to missed it forever.
Without a second thought, I pre-ordered two copies of Neil Gaiman's The Ocean at the End of the Lane signed editions.
Here's the product link if you're interested to buy:
http://www.barnesandnoble.com/w/the-ocean-at-the-end-of-the-lane-gaiman-neil/1114796840
Additionally, Neil Gaiman himself confirmed he will signed those book listed in Barnes & Noble; see his tweet below:
https://twitter.com/neilhimself/status/319522293644668928
Thanks!