Thanks for sharing your concern.
first of all thanks for giving complete history.
please do not worry at all,if th echild is taking normal diet and drinks.also if child appears active as previous then there is nothing to worry.
, it takes little time to get back to old routine.you have not mentioned the cause for anesthesia for your little one?
undigested food particles is due to inadequate chewing in the mouth.please see the child takes food properly.
Also give plenty of fluids and juices,so that the child is not dehydrated.
If the symptoms still persists then it is good to see your pediatrician
Hope it helps.