With all the cells capped and no eggs, I would assume the queen is gone with a swarm. A strong hive can look normal after a swarm. The cells don't all get laid at once, so all of them capped would mean the first one could probably have been capped several days before the others. Since you already split, take down all the cells but a couple of the nicest looking ones in the main hive to help prevent any after swarms, which would mean more lost bees. Treat them carefully. If it's a strong hive, you could have an after swarm or two with virgin queens when they emerge. Did you put a capped queen cell in the split? Do that if you didn't.
If you know anyone needing queen cells, you can give some away if you want. The split would be a better assurance you get a queen with two chances. If they both succeed and you don't want another hive, you can sell or give away the split.
One thing to note, if you have a colony ready to swarm, the only split that will prevent a swarm is one that you take the queen away from the hive. If you can't find the queen, just taking some bees away won't generally stop anything.