The photo printed on the mobile phone case showed the back view of a couple linking arms as they walked across a bridge.
The phone case was among the personal items recovered during the search for survivors of Lion Air Flight JT610, which crashed on Monday.
An image of the items was shared on Twitter by Indonesia's disaster mitigation agency spokesman Sutopo Purwo Nugroho.
Indonesian social media users, curious about the couple's identity, found the answer on an Instagram account belonging to Ms Ine Yunita Savitri, according to a BBC report.
Ms Savitri, who has since privatised her Instagram account, was not on the flight, but her husband Wahjoe Noegrohantoro was, BBC said. The phone case was his.
Mr Antonius Hartono, his nephew, told BBC he spotted the case after his mother told him that his uncle had been on the plane.
"Every time I see that picture on social media, I feel really sad," Mr Hartono was quoted as saying. "I can't imagine how his wife and children would feel."
He added: "It is very shocking. One week ago, I met him and our big families on vacation. We didn't realise that a week after, he would be gone."
On Facebook, a woman who said she was Mr Noegrohantoro's cousin expressed her condolences and shared a screenshot of Ms Savitri's Instagram post.
The woman, who goes by the name Asthy Kuthy Bhreh Hapsari on Facebook, also shared a photo of the family. She added that she was praying for the family.
The 189 people on board Flight JT610 included two infants, one child, two pilots, six flight attendants and 20 Finance Ministry staff who had attended a commemorative event in Jakarta last Saturday.
The pilot of the plane was identified as Captain Bhavye Suneja, an Indian national, while the co-pilot's name was Harvino. The six cabin crew were Shintia Melina, Citra Noivita Anggelia, Alviani Hidayatul Solikha, Damayanti Simarmata, Mery Yulianda and Deny Maula.
Ms Solikha's Instagram account saw a spike in followers after news broke that she was on the Lion Air flight. There were close to 36,000 followers yesterday, up from 2,000.
According to Indonesian newspaper Kompas, Ms Solikha had posted a story on Instagram three hours before the flight. She is believed to have started flying two months ago. In July, she shared two photos of her and her colleagues on an aircraft.
In the posts, she thanked them for their guidance. She also said she was not perfect, but that she wanted to enjoy every moment of her life, and smile whether it was a good or bad situation.