Katheryn Deprill became known as the 'Burger King Baby' after she was found wrapped in a shirt and crying on the bathroom floor of the restaurant in Allentown, Pennsylvania by a customer.
On Sunday, the 27-year-old from South Whitehall Township, posted a photo to Facebook of her holding a message asking for help - and it has since been shared thousands of times.
'Looking for my birth mother,' it reads. 'She gave birth to me September 15th 1986. She abandoned me in the Burger King bathroom only hours old (in) Allentown, Pa.
'Please help me find her by sharing my post. Maybe she will see this. Thank you.'
Deprill, who was about three hours old when she was found, was adopted by a local foster family and she has since gone on to marry, work as an emergency medical technician and have three children of her own.
She told WFMZ that she wanted to find her birth mother to ask questions she had always had about that day - and because she had always wondering if she had any siblings.
'I really want to see her and just ask her why and see if I have any brothers and sisters and anyone that looks like me,' Deprill said.
She added that she did not have any bitterness towards her mother especially because, now as a mother herself, she understood the expense of children.
'I would guess she just couldn't give me the life that she wanted, which is why she left me in a warm, public place,' she added.
In a message to her birth mother, she said that she did not want anything other than to say hello - and maybe have a hug.
'I just want to see you,' she said. 'I want to say thank you for not throwing me away, literally.'
Deprill's adoptive mother Brenda Hollis said she fully supported her daughter's plan.
'I think it's just kind of fun, like there's so many questions to be asked and it's just, I am so excited about it,' she told WFMZ.
A massive search was launched to find Deprill's mother after she was dumped in the Burger King, which is still standing in Allentown.
A worker told police he could remember seeing just one person who might fit the profile: a woman in her early 20s, with collar-length, frizzy sandy brown hair, the Morning Call reported.
He added that she was driving a blue 1970s car and that she'd headed south after leaving.
At the hospital, a nurse guessed that the baby was probably about three hours old. From how the umbilical cord was tied, investigators guessed that whoever delivered the baby had done so before.
Investigators dusted for fingerprints, searched trash cans, interviewed witnesses and followed up on seemingly promising tips - but nothing led them to the mother.
Deprill hopes that social media will turn up what investigators could not all those years ago.
She added: 'I just hope that I can see her and maybe give her a hug.'