Here is a taste of what you missed from my OSINT course held by the Texas Association of Licensed Investigators at the South Texas Midwinter Conference.
Investigators learned how to gather evidence online and keep it admissible in court. (Spoiler: Screenshots may not cut it.) They learned how to build an identity for an investigation subject based on existence, transactions, and behavior using only open sources.
They learned how to conduct more refined web searches and how to use the internet to structure their case, identify leads, and corroborate evidence. Investigators avoided fields of rabbit holes and were introduced to advanced OSINT tools to find what people are selling, what people are saying, what people just said, and where else an image may appear. (By people, I also mean bots.)
Investigators also learned about one of my favorite OSINT tools that helps determine whether photos or videos have been faked. They saw how OSINTers (it's a word) came together and collaborated anonymously to achieve a common goal using flight trackers, wind patterns, and a truck horn.
I did say it was a taste. OSINT is a military term for intelligence gathered openly (i.e.without conducting covert operations), but has been appropriated to mean publicly available and all things from the internet.