A few days ago, I got two more Wemo switches. When I added the switches to the Wemo app, I just named them by their network ID which is just a 3 digit hex number. I did this because I did not decide where I was going to use them yet.
The first thing I noticed is that Alexa automatically recognized these two new Wemo devices without having to say "find my devices."
Since then, I connected one Wemo switch to the outside walkway lights and the other to a light in the garage. Then I changed the name of the devices in the Wemo app to Walkway Light and Garage Light.
Last night as I was laying in bed, I opened the Alexa app and looked at the names of the two Wemo switches. Alexa still knew them as the 3 digit hex number. Whenever you ask Alexa to "find my devices" she announces some useless information on every Echo in the house (we have 4 now). People were sleeping, so I figured I would do that later.
It is a surprise to me that I didn't have to say "find my devices." Alexa got the new names all by herself.