Artboard Issue

[Global Growth22472567e5o6]

I've received my source files back from my designer, which contains a white section that I cannot remove. It doesn't appear to be a part of the artboard, and when I unlock all the layers, I still cannot highlight it to delete it. As you can see from the image, I've unlocked everything in the layers tab. I've also tried hiding things to no avail. 

[rob day]

I opened your packaged .idml in CC2021.