I had this happen and it was a phasing issue. The Dreamseed Cache for the Flourishing Scurfpea appeared just now (days later) when Sprucecrown walked nearby during the Superbloom. I don’t know why it was put into that phase, since I didn’t plant it in that phase, but I’ll take it.
EDIT Blizz has hotfixed: WoW Hotfixes - November 10 - #17 by Linxy