One of my earlier startups, I was a junior/mid level software engineer. I took a skive day to WFH, but was actually travelling to a gig on the train. I sketched out something to pretend I was working that day, and sent him a photo of it. We ended up shipping that design and I only really made one major mistake that we fixed in v2.

It’s amazing how much value there is in idleness.

Rich Hickey, creator of clojure, literally calls this "Hammock driven development" and has a great talk on the matter (multiple actually):

https://www.youtube.com/watch?v=f84n5oFoZBc

(oops, cross-posted with a similar comment.. well, shows the vid is watchworthy)

Update: this person has been fired for "slacking off". The manager only saw the absence, not the work output.

Rich Hickey gave a great talk on Hammock Driven Development