You can put the caged queen on the top bars of the suspect nuc. In about 10 minutes, it should be obvious if that nuc believes itself to be queen-right. If bees raise their abdomens and fan while facing the cage like prayers to Mecca, they are accepting the queen. If they bite the cage and attempt to sting it, they are rejecting. No need to troll through the frames looking for a queen, if you learn to watch the bee behavior.