Not just a head injury, this can easily happen if you find your keychain 10 or 20 years later. I don't think that there is a good solution to it. Maybe biometric data, but then again, I want to have a control over when my data is accessed and in many countries it's legal for law enforcement to make you use your finger or face..
There is. Put it on a piece of paper in a safe place.
Maybe write down my master password and put it in a safe?
Isn't this just moving the goalpost because what if you forget safe combination?
If the Youtube videos I've seen are to be believed then many domestic safes can be broken rather quickly with the right tools,
Safes with electronic locks typically have (backup) keys too, which you'd need to hide or put in another safe, in case the battery dies.
If you write down your master password and put it in a safe you own you can get in that safe wether by code, key, or destructive entry.