My basset, Georgie, hid a milk bone dog biscuit when we were packing the car to visit in laws for 2 weeks. We took our dogs with us and when we returned, I opened the door to let the dogs into the house and Georgie immediately ran upstairs to get the biscuit he hid in my husband’s shoe.
They remember.
Your example is one that actually contradicts the study findings, unlike some of the others here. The study’s point is that dogs can learn from experience, but cannot access specific memories— in particular of the events leading to the learned behavior. I’ve got another, my dog sees/finds a particular animal (racoon, possum, injured bird) in the yard in early evening when I put her out. The next morning, she remembers this particular episode and eagerly waits to go outside, and then races out to that exact spot to see if they are still there. When they are not, she realizes the animal has gone and does not try to do this again. Another example, I put my dogs favorite bone/toy out of reach/sight/smell because she won’t stop playing/chewing and I need sleep. She sees me, and knows where I put it. Several days later (even weeks) she will remember and suddenly remind me by looking at that spot and crying- even though i myself have long since forgotten... lol. They do indeed remember, and have some ability to access those memories.