Wait Until Dark Plot Holes

I recently revisited this film for the first time since it was released in 1967. There seems to be much discussion about the plot holes in the film. One that I don't see mentioned is how do Lisa and Roat know the location of the apartment? Sam and Lisa have a very quick encounter when she gives the doll to Sam at the airport. It's obvious that Sam just wants to get away from her quickly and she just walks away leaving him with the doll. He says no more than a few words to her in the encounter so obviously doesn't give her information about the location of the apartment. So how do Lisa and Roat know the location of the apartment, how do they get in (Does Susie leave it perpetually unlocked) and how do they know that Sam and Susie will not be home.