SOLVED: Why does my background disappear when i add a layer mask

[lambosvt]

I am still learning affinity photo, and one thing that i cant figure out is why the background disappears when i put on the layer mask. I tried doing it with another image, and it worked just fine, but with this certain image (which i have edited) adding a layer mask simply removes the whole background. Can someone explain why that is, and how to get around the problem?

 

 

Edit: I just duplicated the background layer, and now the mask works... but this leaves me questioning as to why it didnt work with the original background layer? 

 

EDIT: SOLVED: So i just right clicked one the original background and for some reason, it was on hide, so i unclicked the hide button.