Apple Watch pinged a phone that is not mine. Why, how do I replicate, and how do I avoid? This morning I used my Apple Watch to locate my iPhone.  Swipe up, tap the phone icon, and somewhere in the caverns of my couch a phone chimes.  After flipping cushions and digging through crevices, I disassembled the entire couch with a sawzall and found my wife's phone.  (Which made me question whether my hearing was off, so I pressed the button again, and it chimed again.) Her phone repeatedly responding to my watch.  I picked up her phone and started rummaging around again for mine.  Decided to try pinging it again, and my phone finally did beep, in the kitchen.

Why was my watch, paired only to my phone, able to make another phone beep?
While it was inconvenient at the moment and a little worrisome, being able to locate multiple phones in a household with the watch would be could be convenient if I knew how to control it.  How can I specify from the watch, which phone to locate?
The watch only pings one phone in my experience (but many watches can pair and ping to one phone)- the phone it paired to from the Watch app. I would first start by looking at each phone in question - check which watches are paired to which phone.

To confirm, I assume are using this tap to summon the phone.

On the fixing, I always like to unpair the watch on the phone I have as primary. Then back that phone up to iCloud and to disk using Finder / Music / iTunes. That way my health and activity data are all in one backup. Then I re-pair the watch with the phone I prefer.