^Of course 12 stares straight at Missy and doesn't know who she is, and Ten wanders around London while Harold Saxon busily building up his political career and doesn't sense his presence. Plus all those times the Doctor (usually Five) doesn't recognise the Master in his cunning disguises 
I suppose it's just possible that the Master's just really good and masking his psychic imprint (or whatever it is)
I've always just worked on the assumption that on a subconscious level the Doctor remembers every face he's ever seen and when regeneration kicks in his subconscious just randomly chooses one?

I suppose it's just possible that the Master's just really good and masking his psychic imprint (or whatever it is)
I've always just worked on the assumption that on a subconscious level the Doctor remembers every face he's ever seen and when regeneration kicks in his subconscious just randomly chooses one?