Funny thing, time. It doesn't always behave as one might expect.
In one strand, Gilderoy Lockhart answers Dumbledore's invitation to teach at Hogwarts with a smile, and immediately stocks up on peacock feather quills.
Pause. Rewind. Watch a butterfly named Jay flap his wings.
Not literal wings, of course. Jay ain't actually a butterfly, a fairy, or anything else Kay might mutter under his breath when Jay relays the differences he notices in their agent roster to Oh.
In this strand, Dumbledore's owl misses Gilderoy Lockhart by a few hours. His potential professor has caught a long-distance portkey to New York, following a promising lead on another novel's worth of fascinating memories. Gilderoy doesn't anticipate any trouble acquiring them; he's been informed the current owners are Muggles. He heads for a building marked Triborough Bridge and Tunnel Authority, daydreaming about the notoriety he'll receive for 'Tea-Time with Talaxians'.
Dumbledore frowns when the owl returns empty-clawed, and reluctantly crosses Gilderoy Lockhart off his list.
The Americans, as is their wont, behave in a rather more contrary fashion. Two days later, Agent Gee walks back out of the ventilation building, wearing black dress robes, a strange new silvery wand, and a smile.