While walking along the street with my dog I noticed someody in front of me had his rucksack half open, so I advised him to close it. It turned out he was from the USA and we exchanged a couple of pleasantries. I immediately forgot about this incident, that lasted no more than a minute or two.
Four days later when I was walking with Lorka in another (busy!) part of the city suddenly she decided to greet a stranger. Naturally I didn't recognize him, he was dressed differently and accompanied by a few other people, whom she ignored. Remembering that vlcaks are very rational I quickly tried to analyse the situation and .... recognized the rucksack.
After a while he recognized Lorka :P
Incredible scent memory!