Maybe. But wasn't it said that Susan is a basically shy person, not really very outgoing?? If that is true, I am not so sure she would have talked to anyone, not even a clerk at a store. Reason I say this is, I am by no means shy nor withdrawn, but it depends entirely on my mood that day whether I talk to people when out and about. I can buy a whole 2 weeks' worth of groceries and never exchange 3 words with the clerk. Some days I just don't feel like talking. Other days, depending on which checker I get, we will talk the whole time I'm checking out.
Also, even if she is a regular customer, if there is a new clerk, they may not remember her because she is basically shy. When you see hundreds of people every day, it's hard to remember one individual, unless they are unique in some way. Even if she did stand out for some reason, a clerk may not remember specifically which day she saw her.