This is indeed what happens when you set up such a value list and sort on column 2--the duplicate values don't appear. If you think about it, this is not so bad a thing. If you saw "Smith John" twice in your list, how would you choose between the two individuals with no other information to know which is the correct "Smith John"?
Here's a work around that looks up ID values, and uses an auto-complete name based drop down that may serve as a better approach for you: Tutorial: How to use an auto-complete drop down list when selecting records related by ID number
The answer, from my past experience, is to create a calculation which concatenates something unique along with the name, such as:
FullName & "|" & email
... or name and phone or street address ...
System would still insert the ID but you would only need to display the second field and there wouldn't be a question on which to use (or you could verify with the customer while they were on the phone, such as "So Mr. Smith, you live on West 54th or on Bradley Avenue?"
I created a calculation that concatenates the customer's full name + their full address and used this in my value list and it worked beautifully! The other solution was way too complicated and above my expertise at this point.