In general, your Hestan Cue cookware, Cue-Enaled cooktop, and mobile device (phone/tablet) should be within 5 feet of each other for an optimal (Bluetooth) connection while cooking. Your internet router should also be close enough such that your mobile device has "full" Wi-Fi internet bars.
That being said, it's possible to maintain a Bluetooth connection several hundred feet away (depending on a number of variables). Though cooking at this range is NOT possible, it would explain why a "far away" cookware is still being detected (example: your Cue pan is in the 3rd floor attic, while your kitchen is on the first floor). To make Cue hardware completely undetectable, you'd need to remove the battery from cookware or disconnect Cue-Enabled cooktops from the electrical current.