I've accepted that I'm always going to be absent-minded to a certain extent, and I've also accepted that I need an uncluttered environment in order to function and that's non-negotiable: home, office, stable, wherever. Not a spartan environment, but uncluttered and visually not "busy." That way even if things are a little messy, it's easier to find the item I'm looking for because it's the thing that isn't usually in that spot. To me it's more efficient to set aside a little time now and then and just organize than it is to minimize space and possessions; I find more living space works better than less because there's more open space. I know I won't fill it just to fill it because my ability to function would plummet.
Can you set out everything you need the night before? Make a list, tape it to the front door, get up earlier to double or triple check everything before you leave?
Are you particularly stressed out right now - I mean aside from losing the keys - or over-scheduled? Lots of stress can throw anyone off their game. Also, snow can be mean. Forgive yourself for misplacing the keys.
P.S. I tried really hard to find some online pictures to illustrate my first paragraph but they were all so dreary and beige they almost left me a little depressed. The closest I could come to what I was trying to describe was this:
As opposed to this, which nearly gave me a heart attack just by looking at it. I could find keys in the above room. I couldn't find my own neck in the one below. I'm not even sure I could force myself to enter it:

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