Rob-Roy

I had a look thru my hives, this glorious warm and sunny afternoon in south Ayrshire, of which I have 4; Starting off the year with 2 hives and watching them progress thru the warm April to near swarming stage I decided to artificially swarm them. This went quite surprisingly smoothly with a few silly errors tooooo silly to post.
However I believe that 1 of the hives had it in its mind to swarm so it did and left me with more or less a neuk of beez, on the original site, with no Queen but they did what they did with a little sugar syrup feeding and reared a new Queen and are progressing just fine The artificial swarm is doing just fine as well.The other hive artificially swarmed and all going well but last week for some reason I couldn't find any eggs or brood. I did find an opened Queen cell and thought that all would be well and there would be a virgin Queen out having a ball and all would be well in a few days. However this afternoon I inspected the aforementioned hive and I find it still Queenless. Why is it Queenless because apart from not finding a Queen, and my Queen finding talents are not that great, there is no egg laying and no brood. !!!!!!!
Now this hive has a lot of bees, a lot of pollen, a fair amount of honey not yet sealed, the bees are enjoying the warmer sunny and dryer conditions of the past few days and are working as well as the other 3 hives in the apiary. What should I do???
Should advertise for a Queen and requeen it?
Should I take a frame of sealed brood from another hive, of which there are plenty, and put it in the Queenless hive?
Should I wait for the Queencup that I found, with an egg in the bottom, and wait for the emergant virgin to return, mated?

Any advice would be welcome, thank you.