I looked into the answer for this question and in most of the answers, I found that it is not possible to detect the iBeacon without knowing the UUID of the device.
But some of the apps on App Store is doing the same. Here are the links for those apps, which are detecting unknown iBeacons.
Let me know if it is possible to detect the unknown iBeacon.
Thanks in advance.
I am the author of the Locate Beacon you mention in the question and its replacement app Beacon Scope. I can assure you that it must know the ProximityUUIDs up front in order to detect beacons. The app is pre-configured with a dozen or so UUIDs (Estimote's default UUID is one of these) so you can detect those beacons without first manually entering the UUID. We do this to make it as easy as possible on the user. (Obviously that worked as you did not even notice we were doing it. Thanks for the compliment!)
You can see these pre-configured UUIDs by going to tge app Settings, which also allows you to enter more.
In the past there have been private APIs that allow you to detect any beacon on iOS. But there are three problems with these: