I agree it is the aquartists responsibility to research the fish, or animal they are buying. You honestly, stores should provide some information as well, just so the buyer can know more.
Interesting, I've had betta eggs hatch after 36 hours. Perhaps, you should have left the female betta in longer.
There is a great Betta Site you can go to with tons of Betta Articles
www.bettysplendens.com
I would be quite tempted to buy it. Only thing is, they are somewhat over-priced in my opinion, and I would think of it as a set-up. I would probably not buy it, and keep quiet.