Oh,Oh sorry Frenchy,my memory is often in la-la-land
Aniroc,like 14+ mentioned,it is very likely your other kitty is also peeing,we used to blame Rocky all the time,until I caught my Chico in the act
Realizing you are in a smallish apartment,it's not possible to limit access for the cats,like I had to do,but hopefully you can at least keep the bed-room closed.