The workman left his phone and pass card in his vehicle - so had no way of calling anyone about his embarrassing predicament.
A workman trapped inside a cash machine was forced to pass handwritten notes through the receipt slot to summon help - but customers thought it was a joke.
He became stuck when changing a lock to a room that leads to the back of the ATM, said police in Corpus Christi, Texas.
Lieutenant Chris Hooper said: "Apparently he left his cellphone and the swipe card he needed to get out of the room outside in his truck."
When he realised he was trapped with no way to communicate, he resorted to sliding notes through the slot.
One read: "Please help. I'm stuck in here and I don't have my phone. Please call my boss ..."
People withdrawing cash though it was a prank, but luckily one called police who heard a faint voice from inside the machine.
They kicked down the door and freed the red-faced worker - his name has so far not been released.
Corpus Christi police officer Richard Olden summed up the bizarre incident: "You'll never see this again in your life th