Home WiFi suddenly not showing on network list

My mother has a computer in the living room and the internet/router is plugged in it and I've used it for mobile devices and laptops for years now without any problem.

Until today.

So now I have a computer in my bedroom (not a laptop, an actual computer, but my old laptop was also used in my bedroom fyi) and when I had left for work at 11am everything was fine, I put my computer to sleep and left, like I always do when I go to work.

When I came back home at 4:30pm and woke my computer up, it wasn't automatically connected like it usually was. So I opened the network list to manually do it and the home wifi wasn't even on the list anymore. I went to the living room to check the modem and router and EVERYTHING was A-OKAY, all plugged in properly, all working, etc. I checked on my android mobile and the home network was listed as "not in range" and so did my mother's mobile (we both have the same phone model).

PS: I work on Windows 8.1