Don't worry that you didn't find brood, look at what they are doing now. There are a number of reasons we could speculate as to why you didn't see brood but now focus on what's in the nuc.
Feed them and gauge their progress. As Jim mentioned a good sign is bringing in pollen but give them some time and then go through the nuc to see what's happening, eggs larvae, that's what you are looking for as well as a queen.
...JP