The Cherries had appeared to be coasting to victory thanks to a brace from Marc Pugh.
The midfielder gave his side the perfect start after just two minutes when he cut in from the left and sent in a powerful shot from 22 yards which bounced down from the crossbar and into the net.
Orient striker Scott McGleish hit the crossbar from six yards eight minutes later, but it was the visitors who struck again when Pugh drove in his second three minutes into the second-half.
However, they lost keeper Shwan Jalal to a facial injury and with five minutes left substitute Jon Stewart was picking the ball out of the net after Tehoue had raced onto a pass from Aaron Brown.
Then, a minute into added time, Tehoue capitalised on a misunderstanding between Stewart and fellow substitute Marvin Bartley to net the equaliser.