From the referenced thread(emphasis added):

On the 15th of April I found a yellow post-it note in a handwriting that wasn't mine on my desk reminding me of some errands I had to do, but told literally nobody about. While odd, I chalked it up to something I did in my sleep, thinking maybe in my half-awake state I scrawled it so it didn't appear to be my handwriting. I threw it out and thought little of it.

On the 19th, I found another post it note on the back of my desk chair, in the same handwriting as the previous note, telling me to make sure I "saved my documents". I was freaked out, but there were no other signs of a break-in, so I set up a web-cam in my house aimed at my desk and used a security-cam app for it to record after detecting movement.

On the 28th, I woke up to find another post-it note, this one saying, "Our landlord isn't letting me talk to you, but it's important we do." I immediately checked the webcam's folder on my computer and found nothing from the night before, but my computer's recycling bin had been emptied, which I am certain I did not do recently, indicating someone had noticed the webcam and deleted the files. (They were just saved straight to a folder on my desktop called "Webcam".

It's happened before here on Reddit: Get yourself a carbon monoxide monitor, you may be suffering from carbon monoxide poisoning. One of the symptoms is leaving yourself notes and not remembering writing them.