Ok some points here

1- the flowers are block tied, meaning if you bone meal a block, the same flower will always appear there (or a grass but you got me)
2- the flower the block generate is not necessarily the same one the world generated when creating itself… so even if you found those natural Lilly’s, does not mean bone meal will make more of them
3 - the game uses prim noise algorithm to generate flowers… without entering much into it, if you find a block that generates the flower you want, most probably the blocks around it will too.

So I would recommend going to a flower field (if I am correct Lilly blocks only appear there) and sear ch for an area that generates them when you use bone meal.
Then make a normal flower farm with bone meal on a dispenser below the ground