I used to frequently leave my keys places. It happens much less now that I have a car. And shh, don't tell anyone, but where my parents live, we don't lock all of our doors - so I don't need to worry about getting locked out.
HOWEVER, once upon a time, when I was starting a New Job, I was given my laptop (standard) and desk keys (which I had previously not used, being a primarily-work-from-home-r). Within about two weeks, I managed to forget my laptop at home. While I was able to work around it for the day, I was determined not to do THAT again. I adopted a new policy of locking my laptop in my desk overnight. (Perhaps negating the purpose of having a laptop, but when you tell me in the interview I can work from home and then tell me on the job I can't, I'm not inclined to bring the laptop home anyway.)
Within a few days of adopting this new policy I managed to forget my desk keys at home. No one in the office had a spare. And, of course, my laptop was safely locked away. So for a day I had to kick mournfully at my desk, cursing myself for looking like an idiot, and use the super-old public buggy computer all day again.
After that I started taking my laptop home and also stopped locking my desk.
Amazingly, this was only the first time I managed to forget my laptop at home. The other time I "forgot" it, though. :) That was a different job.
As for every day situations I frequently am not prepared for - I frequently have head colds and almost never have tissues or a handkerchief, let alone cold medicine/decongestant.