I was flying around in a new world in creative mode. Was looking for a certain type of biome, and had set the gamerules of doMobSpawning and doDaylightCycle to false.

My computer has been quite slow recently, so when I flew through new, previously unexplored, parts of the map the computer was really working hard.

Suddenly, I spotted a pink-black checkered box laying on the ground, in its dropped form. So I picked it up and it turned out to be seeds.

So, I'm not quite sure how you would recreate it as it happened at a very laggy point. But I guess "fly around in creative with your settings way to high" is as good a instruction as I can write.