Hi,
My cat Tansy is 21 yrs old, and she does exactly the same, wanders off upstairs, and miaows until I call her. I think perhaps as she's got older, she sets off where she wants to go, and then gets a bit confused as to where I am. In the last year, she even wanders off into the kitchen when I'm in the living room, and does the miaowing there, either until I call her, or I go to look where she is. As you say your cat is about 14 yrs, which vets consider to be quite elderly, I wonder if the cats (yours and mine), feel the need for reassurance that we are not far away. Im glad your cat is doing so well and is still active. Good luck.