Now he's back home in Van Buren, Arkansas, saying he doesn't remember what followed the graduation party.
"I can't recall anything," Pacheco, 29, told media Sunday back home, with his mother and a cousin. "I mean, it was just a complete blackout.
"Graduation was amazing, all my family and friends were there. Next thing you know (I) blacked out and then ended up showing up back home."
Pacheco went missing June 15, shortly after graduating from the medical school at Universidad Autónoma de Guadalajara, KARK reported. His friend, Carlos Alejandro Delgadillo Romero, was found beaten, shot and killed near the bar where the two were last seen, according to Francine Solis, a cousin of Pacheco's.
"Carlos was a close friend of mine and I'm sorry it happened to him," Pacheco said. "I would have taken his place. He didn't deserve it."
Authorities saw Pacheco on airport surveillance cameras Friday leaving Mexico with his mother, the TV station reported.
Sunday, his family would not discuss how he was found.
"I didn't think I was going to be back home. I thought my life was over, but I'm home," Pacheco said. "I'm just glad I'm home."