A MYSTERY OF DISAPPEARED FLOWERS - Where is the hidden treasure?

Boy Scouts David and Grace had an important mission. In March they were tasked with hiding a treasure in a forest for their younger friends. They thought of a trail which started at the clubhouse than went across the town and over a footbridge to the forest. The younger mates were supposed to follow azimuth instructions and descriptions of environment. David and Grace chose a beautiful hiding place for the treasure. They hid it into an old tree stump which was surrounded by ornaments made of flowers in blossom of various colours: white anemone, purple fumewort and yellow lesser celandine. Unfortunately, there was a heavy rain few days before the treasure quest and the footbridge to the forest was damaged by flooded stream. The Scouts had to postpone their trailing. The footbridge has not been repaired until the end of May. Then, finally, the junior Scouts could go and find the treasure. They followed the instructions. At the end of the trail where they were supposed to find an old tree stump surrounded by colourful ornaments of flowers, they got into trouble. There were no flowers at all. Where and why they disappeared?