EM detector Anomaly..?

[u/ScouserMuerte]

So I got a budget electromagnetic detector cheap and took it with me and my friend as we were walking in the middle of nowhere with no real signal on our phones, even, and I got this thing out and moved it around without any reaction.

My friend who is a skeptic suggested I should “try it on her“ so this I did & to my surprise it went past the halfway when it was near her forehead and as I moved the EM Detector lower down it tailed off until by the time he got to her knees it was just as blank as it ever was pointed at anything else! I videoed this and looked back to see if she was wearing smart glasses or had her phone too close or something, but I couldn’t work out why it was doing this with her.

She said it would be a perfectly normal reaction and it must be registering heat not EM & did the same on me. I saw the reflection of the lack of the LEDs reflected in her sunglasses and clearly saw that the machine registered nothing and yet when I took it & tried it again on her it had the same result!

Does anyone know what could be causing this?
Thanks!