Children's book of unsolved mysteries most likely from the 80s.

I had this book as a young child and was obsessed as soon as I was old enough to read it, which places it no later than the 80s or possibly the extreme early 90s. I don't know where it came from. It was in my grandparents book collection, which was probably entirely curated by my grandmother when I was a kid (she worked for Troll, a publishing company at the time, so she had hookups lol).

It was a yellow softcover book, about the width and height of a normal paperback novel if I'm not mistaken, but pretty thin. It was obviously intended for kids. It covered something like 15-30 mysteries, had black and white illustrations for every story, or at least many of them, and probably only had a maximum of 2-3 pages of explanation per story with a bigger font than your typical novel.

I remember it covering bigfoot (and it's possible there was an illustration of him on the cover, but not sure), Loch Ness, the Tunguska explosion, Roanoke, and possibly the Antikythera mechanism, to name a few specific well known mysteries. There were also a few odd ones that the author probably just made up on the spot, like a guy waving to his family across a field and then just vanishing, as if he stepped out of our reality or something.