The article telling how they found out is amazing, def worth the click and read
http://kotaku.com/the-two-year-mystery-is-over-this-is-frog-fractions-2-1790505179
Steam page of Glittermitten Grove
Also, looks like those sigils that were all over indie games for the past two years were indeed related to Frog Fractions 2
EDIT:
http://kotaku.com/the-two-year-mystery-is-over-this-is-frog-fractions-2-1790505179
Frog Fractions 2 has been unearthed. A collective called the Game Detectives discovered the sequel to developer Jim Crawford’s viral, psychedelic browser game inside another Steam game after a two-year hunt.
Glittermitten Grove, released on Steam mid-December, contains Frog Fractions 2, sources report. Its description reads, “Just like the faeries in your garden, we love collecting berries for our prickleberry loaves and finding treasure with our special fribblesham fireworks. Come join us in our faerieland, full of strange adventure!”
Steam page of Glittermitten Grove
Also, looks like those sigils that were all over indie games for the past two years were indeed related to Frog Fractions 2
A humorously complex alternate reality game (ARG) lead up to Frog Fractions 2’s release. It involved 23 other indie games on Steam. Developers hid puzzle pieces inside those games as a part of Crawford’s ARG. The ARG soon bled into real life, at one point involving a letter from a “time traveler” found in a real-life library book in Berkeley, California. The most recent development before today’s release was the unlocking of a mystery box.
EDIT: