K.D.
Don't give up after just one night. My son was the same -- he could open his door with the safety knob and climb over the baby gate. He was also climbing out of his crib. Just be persistent at putting him back to bed when he gets up. At 2, you might want to ditch both the safety knobs and baby gates and start teaching him where is safe for him to go and the rules for opening doors and leaving rooms (like if it's bedtime he has to stay in his room until morning).
Just remember that you have to be consistent and don't start any habits now that you don't want to continue.