I assume from the number of villagers that you had (including the Golden Child) that you were at level 3 of harvesting and that your villagers were fishing. It is possible to lose your villagers under some circumstances. For example, if your farmers got sick and weren't healed (sick villagers don't work). If there was no food, and the game was on fast speed, you could wake up to dead villagers. It would have to be something drastic like that to cause them all to die, though. It's also possible that something else is going on - it's hard to tell without more details.
The Golden Child is supposed to be invincible, so that's probably why he/she survived.
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Barbara
Unicorn
Last Day of Work