Seems very closely linked to MCPE-30147.
If a flower which is inside a layer of snow is washed away by water, the flower does not drop. Flowers not inside snow layers subject to the same treatment are however dropped as items.
MCPE-30148
Flowers in snow being washed away by water results in the flower being deleted forever
Resolved
Fixed
4
(Unassigned)
102578
Confirmed
Tablet - iOS - iPad Air 2
break, daisy, drop, flower, flowing, poppy, rose, snow, tulip, water
1.13.1, 1.2.8.0, 1.2.9.1, 1.2.10.1, 1.2.10.2, ..., 1.4.0.5, 1.4.2.0, 1.11.0.1 Beta, 1.11.0.3 Beta, 1.14.0
1.16.0.64 Beta
Retrieved
Confirmed on Windows 10 1.2.8.0.
Probably duplicates MCPE-30147.