According to his friends, Bryce Faulkner, 23, was preparing to come out to deeply religious family when his mother discovered emails to his boyfriend, who lives in Wisconsin.
He was then given an ultimatum of being kicked out on the street or going into ex-gay therapy, a controversial "cure" for homosexuality through prayer.
Gay rights activists say it does not work and can be emotionally devastating.
Friends say the college student was left with no choice, as his parents took away his phone, his car and his money.
Speaking to PinkNews.co.uk, his boyfriend Travis Swanson, 24, said he was "very worried".
Swanson said: "Bryce was taken to this place on June 15th. The last time I spoke with him was on that day around 4:30am.
"He called me and was crying uncontrollably saying, 'You should have heard the mean and hateful things they said about me. They made me read out loud passages from the Bible'.
"One of the last things he said to me before falling asleep was, 'Promise me you will be strong for me and for us'."
Swanson believes Faulkner may be at an Exodus International ministry in Florida.
He said a friend of the family had heard Faulkner would be in Mississippi for three weeks and then in Florida for 14 months.
Exodus International has six ministries and 16 churches in Florida. Swanson believes Faulkner may be at one in Pensacola.
The church movement promises "freedom from homosexuality through the power of Jesus Christ".
Peterson Toscano, who has campaigned against so-called homosexuality 'cures' after spending 17 years in ex-gay therapy, told PinkNews.co.uk: "Like in the UK, so much of the ex-gay treatment in the US these days, especially for young people, happens under the radar through Christian counsellors, church youth programs and summer camps.
"Parents can wield tremendous pressure on college-aged children, threatening to withhold funding or even to disown their own children unless they submit to the 'de-gaying' process.
"Through the over 1,000 ex-gay survivors in the US and UK I have met through www.beyondexgay.com and in my travels, I have seen firsthand the devastating emotional, psychological and spiritual damage these 'treatments' and theories inflict on people, often derailing their personal and professional development for years.
"The fruits of these so-called treatments are depression, confusion, isolation, and a damaged sense of self. When parents insist that their child receive these unsound and unregulated procedures, they not only harm their relationship with their own child, but also open up their son or daughter to the potential of personal harm."
To support the campaign to find Bryce Faulkner, visit savebryce.ergonomicalministries.org