It was in stores, the stuff about Sapphire being convention-only is an internet myth. The arcade card was a huge flop because it was overpriced initially. Since no one was buying arcade cards, the print run for Sapphire was fairly small.
Eventually the arcade card's price was slashed, and warehouses dumped their inventory on the market. Unfortunately, by then, Sapphire was already sold out. However, all the new arcade card buyers suddenly wanted it, so voila -- ridiculous price inflation ensues!