I often run into the same kind of situation where I’m looking for this way to find my lost Bluetooth headphones. Usually wireless earbuds or something like that they’re nearly impossible to define. I would try playing out loud sounds but I never hear it. I also find a very frustrating to find a much of very exploitative apps on the App Store that are asking for like five or €10 just to get started for one week or cost like €30.
Below is a free to use option that allows you to see the broadcast strength so you can walk around and try to find your device.
nRF Connect Mobile
https://apps.apple.com/fi/app/nrf-connect-for-mobile/id1054362403