Even phones with no sim card will still connect to cell towers to get some basic info like time and to allow 911 calls. It's possible that the phone without service connected to a different carrier than the one with service and the tower it connected to just happened to be in the other county (exactly how far/close are you to the other county?)
On Android there's an app called CellMapper which will let you see what tower your phone is connected to if someone else has mapped it out.
It doesn't have audio - but this app shows active emergency alerts in the US as well as many other countries. You can set to receive alerts for other locations besides your current one. I use it to keep tabs on places where I've got family members. https://play.google.com/store/apps/details?id=de.mdiener.unwetter.gm
Checkout Fake EAS Simulator on the Google Play Store! All features are free and unlocked, and we are actively developing the app, so please feel free to submit any feature requests. We support 40+ different country alert sounds as well
Sure thing! EAS Simulator seems to be a good one store link (but you need to pay on play store) . but theres always the option of other (free) apps on the play store.
Try downloading this app and wait for the next emergency alert. I had to download it when I deleted the original messaging app on my phone (for some reason EAS reception was baked into instead of being baked into Android itself) and it's really reliable. Sometimes I even get alerts faster than other phones. it's meant for Cellular one subscribers but I'm on Verizon and haven't had any issues