I Caught 2 swarms this weekend but 1 of them have had flew the coupe! I was bummend because it was my very first swarm but I had caught one twice the the size the next day. I was so thrilled. I hope they will be there still tomarrow.
Bribe them with cheaper rent. Maybe that will work. Or a queen excluder.
As Allen said, use a queen "includer" between the bottom board and the hive body for 2-3 days until they settle down. This will keep the queen from leaving and still allows the workers to come and go. This is assuming that the queen is too big to get through the excluder.
I learned this last year when I caught a swarm, boxed it, and found nobody was home later in the day. :-D
I rarely if ever have swarms leave the set up I give them, but as others have mentioned a queen excluder will keep them in. You could always remove it after 3-4 days.
...JP
Keep them cooped up for 3 days. Oh yea, feed them.