Alice has misplaced her keys (which rarely happens), but her grandchildren are worried that something might be wrong with her, even though her granddaughter has done the same thing three times this week. the above is an example of

I believe the answer is: age based double standard
age based double standard refers to the occurrence when we interpret a certain event as 'normal' if happen to certain age group but would interpret it as 'worrisome' if it happen to other age group.
in the scenario above, the double standard occur because forgetting something on old age could easily be interpreted as a sign for deteriorating brain.

The correct answer is connotation.