Same issue.
Cultivated Seed had been in my inventory since I got it a few days ago. I didn’t notice anything was wrong today as I upgraded the Personal Story items, but when I arrived at the Mystic Forge, the names of the items I needed didn’t quite match up and lo and behold, I had a Pet Seed in my inventory now.
What a strange problem! I wish ANet luck in trying to figure out what went wrong here!