What is the ruling regarding a husband who threatened his wife with divorce if he did not find his gold chain on the bed, and he intended the threat, then he did not find it?

A husband's statement to his wife, "If I don't find the necklace, I will divorce you," is a promise of divorce that does not entail anything. As for his statement, "You are considered divorced," this is a kinayah (allusive expression), and it does not obligate him to anything if he did not intend divorce by it, but merely a threat.