Unknown Switch that refuses to go!

I have a load of switches and fan controllers and various other bits that are connected. We’re having builders do some remodelling and so yesterday I added two new switches that they fitted. One is a fan controller that controls two fans (one in the walk-in wardrobe and the other in the bathroom). The other is a light that switches the lights on in the bathroom and wardrobe. The lights also have an add-on switch so we can turn them on/off from either room. I’ve added them both just fine and they both work perfectly. I tend to add things one at a time so I know which is which. However, just as I was adding one, another, unknown, switch popped in. I saved this as it come in just as I was clicking Save. I have no idea what this switch is, and we’ve walked the house numerous times trying to see what comes on/off when we press it, but nothing does. Pressing it in the Smartthings app turns it on/off, but nothing in the house seems to come on or off.

Since it’s a ghost, I tried to remove it, but I can’t do that either. I can go through the remove options, and select force remove but the screen just sits there and refuses to remove it. It only appears in the Classic app (circle icon) not the new one (five circle star hub thingie icon).

Any one got any idea how I can get rid of it?