Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Now if he hasn't passed feces in over a day, that is not overly worrying. We can see normal delay in feces up to 36-48 hours. That said, if this is a break from his normal routine, then there are some steps we can take to just encourage him to go while monitoring his behavior relative to the yard (in case this is something in the yard that is making him less then keen to go).
In regards ***** ***** encouragements, you can start by offering some milk. We do find that milk can be helpful at getting things moving along if a dog has mild constipation (though don't be alarmed if this makes his stool a bit loose). As well, cat hairball medication (ie. Catalax, Laxatone, etc) can be used to get things moving. This is available from the vet or the pet shop. It works to lubricate the gut and can facilitate the movement of resistant feces out of the rectum.
Alternatively, you can add a dose of fiber (ie spoonful of canned pumpkin) or a small volume of a GI lubricant (ie Miralax, lactulose or mineral oil) into his food. These just again will help push any resistant stool through and give him the push he needs to go.
So, I would suggest the above for your lad to see if we can just get him to. Of course, while you are doing this, I would advise monitoring and if you try the above but are not seeing feces in the next 12-24 hours, or your lad begins to vomit, show belly pain, or worsens, then they should be evaluated by a vet. While it doesn't sound the case from your history, impactions of feces sometimes won’t respond to our gentle colon cleaning treatments, and those cases can require more aggressive treatment (ie enemas under sedation) to clear them out.
All the best,