It was proably not published in a "propper" way, so it's ok. There are bizare idears who is the first to publish something, for example that pre-print don't count, because ... well I don't know.

This was not some amateur discovery. This was 2009 Intel International Engineering Science Fair's top prize for Microbiology category.

I would be surprised if those award winning high schoolers had no assistance from professors to teach them how to do research and write papers.

And here the Stanford paper performed a long term study on mealworms and a styrofoam diet as opposed to a control. As for why they didn't reference the previous discovery, it could be for a couple of reasons:

1. The primary author(s) were not distinctly aware of the discovery.

2. If nothing was published in the 2009 Intel International Engineering Science Fair, then there is little to reference. Referencing a news article in a journal is not often considered good practice, and in many cases can be considered unacceptable.

This is a case where I would say "do not attribute to malice...", as I don't see any direct benefit to the researchers for excluding this reference in their paper. Their study focuses on long-term results, not merely "mealworms can eat styrofoam, news at eleven."

EDIT: Formatting

Again, other than the news article, this is the official winning announcement: https://member.societyforscience.org/document.doc?id=74

I would be very surprised that Intel IESF awarded prize to research projects without a paper! Also, from the links referenced above, I clearly saw the high schooler was presenting in a whiteboard with her research paper with diagrams.

Granted, I am unsure if the paper was published in any established academic journals/magazines etc. or gone through any peer reviews. But considering she was a 16-year-old at the time, with only more than a year of research into this subject matter and with a fairly accurate conclusion.