One of the consultants on the dementia ward I worked in had it spot on......it’s not a problem if you get to the cash point and have forgotten your PIN number. It’s more of a worry however, if you get to the cash point with your card and have no clue what to do with it or why.
Everyday forgetfulness is a part of life, exacerbated often by stress, fatigue, worry, medication etc etc.
When it becomes more of a concern is when folk are unable to process conversations/instructions , forget how to use routine home items , be unable to follow a plot on the tv or in a book, plus many more things, .any of these may then lead to the person beginning to isolate to protect themselves.
Even then however, this could only be a temporary condition of mild cognitive impairment, which doesn’t always progress.
Don’t panic but see your GP if you and your nearest and dearest notice a pattern.