Wiktionary
memory like a sieve
n. (context simile English) (alternative form of mind like a sieve English)
Usage examples of "memory like a sieve".
She'd tell the old aunt in charge of the pantry that she was going out for whatever it was, and since the old aunt had a memory like a sieve net, she wouldn't remember that Menolly had done the same thing the day before or realize that she would do the same the day after.
Frost, who had a memory like a sieve when it came to detail, glanced across the room to make sure Barnard was jotting down the times in his notebook.