I purchased a Diamong ring from a well known jeweler, and was happy looked good from the naked eye.

The statute of limitations in Nevada for common law fraud claims is 3 years from the date that the fraud was actually discovered and should have been discovered.  Torrealba v. Kesmetis, 124 Nev. 95, 97 (2008).  More specifically NRS 11.190(3)(d) provides in pertinent part: "[A]ctions other than those for the recovery of real property, unless further limited by specific statute, may only be commenced as follows: . . . 3.  Within 3 years: . . . .(d) Except as otherwise provided in NRS 112.230 and 166.170, an action for relief on the ground of fraud or mistake, but the cause of action in such a case shall be deemed to accrue upon the discovery by the aggrieved party of the facts constituting the fraud or mistake." The statute hinges on notice of the fraud.  “When [a person] knew or in the exercise of proper diligence should have known of the facts constituting the elements of his cause of action is a question of fact for the trier of fact.” Oak Grove Inv. v. Bell & Gossett Co., 99 Nev. 616, 623, 668 P.2d 1075, 1079 (1983); Nevada Power Co. v. Monsanto Co., 955 F.2d 1304, 1307 (9th Cir. 1992). You have indicated that you purchased the diamond 4 years ago, which may cause problems in the ability to prove a fraud claim.  However you have a backup remedy which is that the statute of limitations for breach of a written contract is 6 years, as well as an unwritten agreement being 4 years.  A breach of contract claim might provide the extended statute of limitations which you need under the peculiar facts in your case, in light of the fact that you were not given the merchandise which you were promised.