I definitely think that you should call Tesla service. My wife and I each have access to each other's cars from our individual accounts. It works like you described by swiping back and forth on the car icon in the app. But this had to be set up by contacting Tesla's 800 number and then there was a 2 factor authentication step (by email IIRC). I'd be worried that the owner of VESA has access to your car too. That's not necessarily true but it's a concern. If someone does have your car on their account (again a remote chance but you have access to their car), then they can see the location of your car in their app too. My guess is that someone at Tesla fat-fingered a VIN or something when they set up shared access like my wife and I have.
This is concerning in general because all of us are relying on Tesla not screwing this up for the security of our cars. If you do call them, would you please report back here to let us know what they say about it? If I was VESA's owner, I'd be pretty angry about this.
