There is not one French Crown, there were actually 20 of them stashed at the Basilica of Saint-Denis where the vast majority of French kings and their close family are buried.

The crown displayed at the Louvres Museum is unfortunately the only one from the pre-Revolution era (Ancient Régime) that was spared by the revolutionnaries when they sacked the Basilica :

After the French Revolution (1789), and during Robespierre's Reign of Terror (1793-1794), the French National Convention ordains the exhumation and destruction of all royal tombs. In October 1793, the profanation of the tombs at the Basilica of Saint Denis is executed. This basilica has been the necropolis for the kings and queens of France since the burial there of King Dagobert in c639. In total, over 170 bodies are exhumed, mutilated and spread over two common graves just outside the basilica. In 1817, the unidentifiable remains are recovered from these common graves, and re-burried in the basilica in ten joint coffins.

The crown you saw is probably the one that belonged to Louis XV but we have plenty other items that are considered a part of the French Crown Jewels collection like Napoleon and Josephine's Crowns (yes, 11 years after they pillaged the Basilica, we had someone crowning himself Emperor of France and taking full control of the country ...)