As if that weren't strange enough, creatures like beetles and moths, which would usually be expected to attack the unguarded boxes of golden liquid, stayed away.
This mysterious phenomenon called colony collapse disorder has existed since 2006, but was at its worst in the US and Europe last year.
Though the problem has yet hit Hong Kong's bee farms, students at Kellett School decided to highlight the plight of the foragers by organising Buzz Day last month.
Dressed in yellow and black, students from Primary One and Six used morning assembly to teach other students what would happen in a world without bees.
They also stuck posters they had designed around the campus to raise awareness.
"If we don't have bees, we'll lose our food supplies," says Eliza Sherry, a Primary Six student, who proposed the campaign.
One of every three bites of food eaten worldwide depends on pollinators, especially bees. To enjoy fruits and vegetables - from strawberries to almonds and cabbage - first we need honeybees to pollinate the flowers.
Eliza's schoolmate, Daisy Collins, says the problem affects the entire food chain. Restaurants might no longer serve steaks, burger or pizzas because cows would not have grass to feed on, she says.
The students have learned from classes and research that scientists have been looking for the cause of colony collapse disorder, but are not sure what is responsible.
One possible culprit is a parasite called the varroa mite. It infects worker bees and sucks their blood. Angus Pittar, one of the young campaigners, says the infection spreads quickly in the colony and could cause the next generation of bees to be born with abnormalities, such as wings that can't be used fly.
Eliza believes neonicotinoid pesticides could be another cause. The nicotine-related chemical protects crops against pests, but harms pollinators. It is highly toxic to bees and can paralyse and kill them.
Modern life could take a toll on bee's mental health, too, says fellow environmentalist Tej Sheopuri. Commercial beekeepers, who keep colonies to pollinate crops, often move hives from farm to farm on trucks. Bees become stressed when they're moved often.
A lack of genetic diversity can make bees increasingly susceptible to any pest or disease, says teacher Beth McNeilly, who introduced the subject to students in class. "Beekeepers can order captive-bred queen bees by mail," she said. "But when laboratories use the same DNA over and over, it won't be strong and resistant enough to defend [itself]."
The students say there are simple things Hongkongers can do to keep honeybees buzzing.
For example, Angus proposes we plant bee-friendly flowers, stop using pesticides and build "easy bee hotels", with bamboo sticks.