Until you have experienced something that defies normal explanation, it’s safer to keep an open mind. I assure you, this is just one encounter of many.
I’ve seen two people approaching, they pass deep in conversation and then when I turned a few seconds later, to call my dog, they had disappeared. There was nowhere for them to go, it was daylight, a long straight road, a high wall on one side which didn’t have openings and on the other side a wide river.
I can’t convince you ghosts exist, even if they aren’t ‘real’ in the worldly sense, but the two people who passed me were quite solid and unremarkable, then a few seconds later they had just vanished into thin air.