The real answer? Their sense of smell.
They can smell when certain scents fade and they use that to tell time.
This is how Murphy reminds me to take my meds at the same time every morning.
I task trained Murphy for SD stuff at around 4 years old after she had already been public access trained for a year or two, so she got to be a regular pet before I made her do a bunch of tasks.
It is inappropriate to give out client information. I would be so mad if my breeder gave my phone number to some random person as a reference.
Also, a breeder probably is not going to call up people they have sold puppies to to ask them to do this kind of thing.
It is a weird ask imo
It really is amazing how they will naturally circle back to you. It is even cooler when you're walking with other dog breeds and notice they just don't do that. The protection genes are strong.