Cult Conscript enters the battlefield tapped.
{1}{B}: Return Cult Conscript from your graveyard to the battlefield. Activate only if a non-Skeleton creature died under your control this turn.
Creature tokens that die are put into your graveyard as normal (and cease to exist soon after). If a non-Skeleton creature token died this turn, it satisfies the activation restriction.
Similarly, Cult Conscript didn’t need to be any specific zone at the time that creature died.
The creature that died doesn’t have to still be in its owner’s graveyard to satisfy the activation restriction.