If you took a couple of frames of bees from a hive with brood, and honey, and put it in a Nuc box in the same bee yard. What happened was your field bees returned to the old hive. There were not enough bees in the Nuc to defend against any outsiders. Furthermore the field bees that returned to the old hive probably returned to the Nuc to rob it out. Did you use a Nuc box/5 frame box or just a ten frame deep? Did you reduce the entrance, or do anything to re-orient the bees?
I know some here have success with placing branches, and such in front of hives, and had good results re-orienting bees, I have not (I am sure this is an operator error). The problem is if you want the Nuc to raise a queeen then you need to be near the bee yard so when the queen goes for her nuptual flight she will have a good number of drones to choose from, and hopefully a broader scope of genetics. So moving the Nuc away with out a queen may not work so well. In addition you set the hive back while waiting for them to produce a queen that may or may not be viable.
I did a cut down split last year, and split a ten frame deep into two colonies in early July. I bought 2 queens $18.00 each, and moved the two new colonies to two seperate bee yards. Both colonies did fine one built up to produce honey the other is fine as of the other day, but had some trouble due to moving from the out yard back home. The one that built up to produce honey was not moved a second time. The one that did not build up as well lost field bees when I brought it back. Theoreticaly I could have made five colonies from ten frames of bees, but they would have taken forever to build up. I think in the future when I do a cut down I will just make one colony that has a better chance of producing than splitting it in two.