passing each other without meeting; just missing each other
Describes two people or things moving in opposite directions and failing to meet, or one arriving just after the other has left. Often used with になる or で.
I missed him because we passed each other without meeting.
My mother had just left when I arrived, so we missed each other.
inserting in the wrong order
Used when items are placed in an incorrect sequence, such as pages in a document or parts in an assembly. Less common than the 'passing each other' sense.
The pages of the document were inserted in the wrong order.