Little aid reached Jabaliya, where they had been staying since fleeing their small home in the early weeks of the conflict, and his children had been reduced to eating wild plants.
So Abu Jalala went out into the darkness to search for flour being brought by a humanitarian convoy.
"We would never have let him go if we'd known ... We've not seen or heard of him since," said Etemad Abu Jalala, the missing man's uncle.
After six months of war, tens of thousands have disappeared in Gaza, their whereabouts unknown to their relatives or friends.
The International Committee of the Red Cross (ICRC) has recorded more than 7,000 calls to its missing persons hotline since the start of the conflict in Gaza but the total is almost certainly many times that figure.
Abu Jalala, who had a chronic psychological illness, has not been seen since the night he left his family in the shelter.
"We go out to search for him every day hoping to find him, but in vain. We hope that he is still alive. We have tried to contact hospitals and the police... but without any results," his brother said.
More than 33,000 people, mostly women and children, have been killed in Gaza so far in the conflict, according to local health officials. Artillery bombardment and airstrikes have reduced entire blocks of flats or tenements to rubble across much of the territory, burying many whose deaths have gone unrecorded.
Some of the dead have been placed in makeshift graves by strangers.
Raji Kamal Kaleel, 36, is still hoping for news of his wife and two-year-old daughter, whom he last saw in January during a period of Israeli shelling and airstrikes in Gaza City.
"When the bombardment intensified on our neighbourhood, we decided to flee to a UN shelter, but on the way there was a big airstrike, and the whole area was filled with black smoke.
"We couldn't see each other so all of us ran in different directions," Kaleel said.
When the smoke cleared, Kaleel found his mother, his 10-yearold son, and his oldest daughter, who is 11, but not his wife or youngest child.
"I lost my closest friend and the mother of my children. Nothing will ever compare," he said. "My life can't continue without her.
And I also lost my little daughter, a part of my heart. People tell me their bodies were vaporised or buried under the ruins, but I still have hope."
Some of the disappeared, especially badly traumatised children or the psychologically ill, may still be alive, but unable to find their relatives after being separated.
Laila Dogmush disappeared when she set out to find her son, who had gone in search of possessions abandoned by her large family as they fled the Israeli offensive, which was triggered by attacks into Israel by Hamas in October that killed 1,200 people, mostly civilians.
"My mother pretended that she wanted to go to the nearby mosque for prayer but didn't appear again," Fidaa Dogmush, the 62-year-old's son, said.
"Her psychological state might have been affected by the successive traumas that she lived through."
Fadi Tambora's mother last saw her 35-year-old son when he set out from a shelter in northern Gaza to join his pregnant wife, who had fled with her family to the south of the territory. In the several weeks since, she has had no news.
"My son is deaf since birth. He asked his father by sign language for money to join his wife but later that same day there was an airstrike and we were all scattered and we lost him," Tambora's mother, who preferred not to give her name, said.
Since then, there has been one sighting of Tambora at a hospital in Jabaliya, and friends found some clothes and possessions nearby. But that was all.
Tambora's mother fears her son may have been shot by Israeli troops after failing to respond to a warning that he could not hear.
"The only wish we have is for him to return to his baby who was just born two months ago," she said.
For many who are searching, the prospect of detention by Israeli troops brings hope that their loved ones are alive, but fears too.
"We think around 1,000 are still imprisoned without charge or notification of relatives bu...