If the facts are as you describe, particularly if you explained your wife's inexperience to them before she started riding and they continued to pressure her to ride, I would be willing to argue that they assumed the risk that she might damage the bike.
If you had just walked out of their place and they were suing you, it would be fairly easy to assert that and get them to accept a nominal amount to be done. Where you have signed a contract to purchase the bike, it is no longer that easy.
Arguably, their approach to this constitutes an unfair or deceptive practice under the Utah Consumer Sales Practices Act. You could file a small claims action against them seeking $2000 under that act and then try to negotiate something where you give back the bike and dismiss your claims.
Before you go that rout, motorcycle dealers are regulated by the Utah Motor Vehicle Enforcement Division which may (or may not) assist you in working this out with the seller. http://mved.utah.gov/ The MVED will probably be able to get a copy of the credit app pretty quickly. If they will not provide that to them they will likely end up in trouble if they are licensed as a dealer.
Best of luck.
Providing this answer does not form an attorney-client relationship. Most legal questions are exceedingly fact-sensitive and therefore this answer is a best-guess based on the information you provide. You should consult an attorney licensed in your state to further discuss your matter.