I agree. If he's not showing other symptoms like not wanting to eat, lethargy or whining then he either did it somewhere you don't know about or he's a bit constipated. It happens to dogs too! A spoonful of canned pumpkin can help with that.
If he IS showing odd symptoms, I would be worried. He may have eaten something that's stuck in his intestines, and that's an emergency. Can you give us any more detailed information?
Don't neglect to check out the possibility that he went and pooped somewhere where you just haven't seen it yet. I have had puppies leave me surprises behind the furniture, etc. If he is acting happy and healthy after not pooping for 30 hours, and he has been eating, then I would start looking for poop in unexpected places. What goes in must come out. A puppy who has truly not pooped in 30 hours will show some sign of illness by now. So if he is playing, happy, and still eating and drinking, then there has got to be some poop, someplace.
Does his belly seem tight or bloated?You could try to give him a 1 or 2 tablespoons of canned pumpkin.It works like a laxative just in case he might be constipated.It works really well for constipation and it doesnt upset there bellys.But like Ginger said above he might have gotten ahold of something and could be obstructed.When ya'll got back home yesterday was there anything that he could have gotten ahold of when you were not around?Alot of times if obstructed they will vomit as well.I hope that he feels better soon.Take care
You have to take him to be checked out by a vet. It could be he has had something happen while you were away...such as chomping on something he shouldn't. He could have an intestinal obstruction possibly. That wouldn't be impossible for a 6-month old, who is into everything!
It IS possible he was upset by your absence. He is very young, and had made a bond with you, then you went away. It might be nothing more than that. Anxiety.
But take him to the vet to be on the safe side.