The ability of Daretti’s emblem will return the artifact card only if it’s still in your graveyard when the delayed triggered ability resolves at the beginning of the next end step. If the artifact card left your graveyard before that point (even if it was put back into your graveyard), the ability won’t return it to the battlefield.

You choose which artifact to sacrifice as the second ability resolves. You must sacrifice an artifact if you control at least one at that time. For example, if you control two artifacts when you activate the second ability, but the artifact you intended to sacrifice is destroyed in response, you must sacrifice the other artifact as the ability resolves.

You may choose to discard zero cards as the first ability resolves. In that case, you won’t draw any cards.