Shared facilities are breeding grounds for confrontations. We see this in gyms when some patrons dominate a machine and refuse to let anybody else use it. But this is even more problematic in the office when someone occupies the toilet for long periods. It’s horrible for other people who are trying to hold it in.
That’s why this person left a passive-aggressive note for one frequent perpetrator. They raised the stakes by sticking it to their nemesis’s laptop screen in an antagonistic move. But it’s a desperate situation so nobody can blame them. The toilet time-waster was probably scrolling on their phone anyway (via Imgur).