Start with links to several of the Salearea Guides. The Costa Rica plant is mentioned in several of them.
Coach has been making handbags in Costa Rica at least since 1994 and as recently as 2004:
http://www.ebay.com/gds/Authentic-Coach-Vintage-and-Classic-Leather-/10000000062579034/g.html
http://www.ebay.com/gds/Coach-Italy-Guide-Coach-Italian-Made-Bags-/10000000051492233/g.html
"The Sheridans were made in Costa Rica and the US as well as Italy and had a more rounded or pebbled leather grain, a taupe fabric lining, and a creed similar to the Dakotas."
http://www.ebay.com/gds/Coach-Authenticity-Guides-Facts-and-Myths-/10000000062607882/g.html
"THE "COACHES ARE ONLY MADE IN..." RULES
Depends. Coach bags have been made in the USA, Italy (a few very expensive exotic leather styles are still made there), Costa Rica, Dominican Republic, Mexico, Hungary, Turkey, Thailand, China, India, and Vietnam. Coach will soon be making bags in the Philippines and other countries where they can find cheap labor, and they have made accessories like wallets in even more places such as France, Spain and others. Other than Italy, only the Asian plants except for Turkey and Thailand are still active at this time (2011). Production moved almost completely to China starting in 2000, and all Signature C fabric bags are only made in China and the other Asian plants and have only been made since 2000. Any Signature C bag with a year code from before 2000, or with a plant code or place of origin that indicates it was made in the US, is counterfeit."
"Coach brought out the Sonoma line in 1994 and while not strictly an Italian line, like the Sheridans many Sonomas were also made in Italy as well as Costa Rica and the US."
The bag in your original listing is completely genuine. The original Penelope line came out in the early 2000s and many used leathers that had a slightly different feel to Coach's original cowhide. Anyone who questions the fact that Coach made bags in Costa Rica doesn't know a darned thing about Coach and doesn't deserve to own one. I've also never seen a fake Coach with a creed that said it was made in Costa Rica. Fakes will almost always say they were made either in the US or, for the more recent ones, in China.
Sorry you and your original buyer got stuck with a Poisonous Buyer, even if it was at a distance.