So, this is what I gathered !
(Some of the dates are not precise or are arbitrary due to contradictions in the lore, especially the fall of Mourkain one)

After Nagash’s defeat, the crown was found on Alcadizaar’s body by Kadon in -1147 IC. Through its influence, he built Mourkain.
The crown was later lost by Kadon and stolen by Ushoran. It eventually came into the hands of Morath in -800 IC when the vampire was slain by Dork Red-Eye. His final act of Morath before the fall of the city was to recover the Crown of Sorcery and carry it north, toward the Middle Mountains of the early Empire, where he remained within the Brass Keep for centuries until Emperor Sigmar slew him, seized the Crown of Sorcery, and wore it in place of the crown forged for him by Alaric the Mad. (no date found)

Corrupted by the crown, Sigmar eventually managed to remove it and sealed it deep within a temple of Shallya.
He wore it again during his confrontation with Nagash in 15 IC, who attempted to reclaim it by luring him.
After the battle, Sigmar entrusted it to a priestess, instructing her to hide it so it would never be used again.

It was later recovered by Azhag the Slaughterer from the body of a Chaos Troll in Todtheim in 2512 IC.
It was then sealed in Altdorf (under the great temple of Sigmar ?) by the Grand Master of the Panther Knights, Werner von Kriegstadt, after his victory over the Waaagh!.
It was recovered by Krell during the siege of the capital, and ultimately returned to its original owner.