Similar story from 1993

"Some of Mr. Lynch's best picks came from watching his three teen-age daughters shop at a nearby mall,..."

https://www.baltimoresun.com/news/bs-xpm-1993-03-09-19930680...

His book, One Up On Wall Street, references this idea of using casual observations to find undervalued stocks. You might find that interesting to look through.

His Book "One up on Wall Street". (which others have mentioned.)