Findley, 25, is a free agent after leaving Real Salt Lake and had been on trial with Premier League side Wolves.
But manager Mick McCarthy told the Birmingham Mail that the ex-LA Galaxy forward has opted to join the Reds.
"We had him for two or three days but he's gone to Forest. I think he's been offered a contract, whereas we wanted to have a look at him," McCarthy said.
Source: BBC Sport
Source: BBC Sport