For those of you that find the Lily difficult to find, I would suggest our meeting meadow.. Dewdrop Vale.
Dewdrop Vale has the most Lily petals down near the water, and many are almost hidden in the lower left corner and the bottom edge. You only see a little of the "glowing" that something is there.
As a side note, for what I presume would apply to all collectibles:
I discovered as I went religiously from one server to the next, covering them all for the Ivy.. (I had already determined which Meadows held the best shot at Ivy) that there were a few Servers that consistently held more Ivy than others. Some Servers didn't have any! So these past few overnights, I went ONLY to those few Servers/Meadows, and the job was SO much more rewarding and less frustrating.
So if you have the time.. take note of which Servers and Meadows hold the most of what you are looking for, and stick with them. (I did notice, but didn't log.. that a few Server's Dewdrop Vale, had at least 10 Lily petals consistently!)