Sometimes queens die. Sometimes it happens in transportation, sometimes she dies in an inspection, sometimes she rolls off a frame. I've had all 3 of these things happen.
Knowing how long things take helps you predict where things are going or where things have been.
If you find eggs, but you can't find her, you know there was a queen 3 days ago. She’s probably still there, you just simply missed her.
If you find a queen cell and it's uncapped, it is less than 8 days old, as the queen cell caps at 8 days. The cell stays capped from 8 days, all the way up to 16 days. After 16 days, the queen will be born and within 8 more days, you should see eggs.
If you killed or lost a queen, how long before you'll have a laying queen again? Approximately 24 days.
If you find a capped queen cell, how long before it should emerge? 8-9 days.
If a queen is killed and the bees raise a new one how much brood will be left in the hive just before the new queen starts to lay? None. It will take 24 days for the new queen to start laying and in 21 days all the workers will have emerged.
If the queen starts laying today, how long before that brood will be foraging for honey? 42 days. Remember the bees get promoted and collecting nectar is the last stage of their lives.
It's unfortunate when your queen dies, but the good news is, they can requeen themselves if there are eggs in your hive!
Another option is to find a mated queen and requeen that way. Sometimes it's hard to find one just at the moment you need her, but if you can, you are definitely speeding up this process!