I recently placed a kitten in a home where a couple were home from work (holidays) and the kitten did fine with the litter box, however, when they went back to work Junior did not use the box and messed on the furniture instead. While they were home Junior was taken to the box (downstairs) by the husband - is there a possibility that once the taxiing was over Junior "couldn't do it?"

What exactly is Taxiing? I'm sorry I don't understand.:confused:

By taxiing I just meant the owner carrying (taxiing) the kitten downstairs to the litter box.

Is the litter box available to the kitten without the taxiing? It is a kitten, does it have to go a long distance down some stairs to get to it?
Just asking. They usually know what to do, if it's available.:)

There isn't any reason that being carried down the stairs would make this kitten not be able to go or change him in any way.

Is it a tiny kitten? Perhaps just too small to get down the stairs, or too much work. Cats are smart, so I suspect he knows where it's at, even if he was carried to it before. But maybe just too difficult for him right now. I'd suggest bringing it upstairs to an easier place until he either grows a bit or gets used to it being there. Perhaps near the stairs so he gets the idea. Then when he can handle it, put it at the bottom of the stairs. After a short time of that, if everything's OK, then it can be moved wherever they want it downstairs.