Hi, welcome to the forum from Louisiana. Glad you joined.
This link takes you to an article in the Articles section above that shows you what to look for when candling. It covers chicken eggs but the general idea is the same for all poultry eggs. The timing will be off though for different species because they take different times to develop.
https://www.backyardchickens.com/articles/development-of-a-chicken-embryo-day-by-day.72537/
I don't have any idea what species of egg that is you found in the forest. How did it get out by itself? It could be about anything: turkey, duck, grouse, snake or many other things. I'm sure there is a story you will never know.
The first thing we usually see is veining. Other stuff can start to show up earlier but it's really hard to see, especially if you have no experience looking. Three days is fairly early to see veining in chickens and if that is something with a longer incubation period it may just be too early. I'd be patient and try again in a couple of days. As good of a view that you have it should be pretty obvious when veining starts.