I read a dragon series like this sorta, where the dragon eggs woukd be hidden for hundreds of years, and they were imoossible to find until it was their time to be found, then it was easier to find them, like they had to sit for 100 years before being found, that's how long it took the dragons to develop inside the egg and then wanna be found so that they could hatch for it took a human to hatch a dragon