They probably just went on Holiday, and had their children (and grandchildren) watch their home while gone ... yep, pretty boring ...
The dog ate the chickens, or ... the children ate the chickens, to see if they really taste like chicken!
The old people got in their space ship and flew back to give a report of their findings. They took the chickens to show what pass as pets for earth people and now on their native planet they are raising chickens. In the meantime they replaced the old people with a newer batch who are closer to the average population. They believe they will blend better.
They are all together now waiting for further instructions from the home planets task coordinator and liaison. It seems they have been failing at socializing with humans so they will soon be making an effort to do better. Lol