Thank you for the additional information.
With a dog this age displaying these symptoms especially the not passing stool and the vomiting with in a short time after eating x rays would be one of the first things that would have been recommended in our office. This is because young dogs are notorious for eating things they should not and it is not uncommon for the owner to not know.
All of these symptoms can be a sign of a gastrointestinal blockage. My concern with waiting for an additional 2 days is that if this is the cause then there is a risk of perforation of the intestines or even dying off of the intestines in the area the object is stuck.
I would suggest going back to the vet tomorrow and ask for x rays. If these are clear then the next step would be blood work to look for problems such as pancreatitis.
Also if they only check the stool in the office then sending it out to the lab would be recommended,
If this was my dog or one of our patients I would say do not wait for 2 days for the x rays I would rather do them sooner and there not be a blockage then to allow it to stay in place for 2 more days if there is.
Here is some additional information on gastrointestinal blockages LInk
If he vomited the food he had last I would not even offer any until you can call your vet in the morning.
I hope this helps. Please reply back if you have additional questions or concerns and I will be happy to continue.