I just went thru the beginning of the game again, and all I have found is "her older sister." That was said in the diner where they first met to discuss the guitar.
And even with a first name, does that mean he is going to jump up and say, "I dated a girl with that name before!"
Now if it were a first and a last name that he recognized, then yeah, he would have said, "Hold on a minute, tell me about her"
Basically he would have asked direct questions, if he had thought that the girl he dated in college was the same person. A first name only, would not prompt such a response. Try googling your own full name and unless you have a strange one, you will find out that you are not alone.
In the state that I live in alone, 70 people have the same first and last name as mine, but there would be thousands with just my first name.
For example, according to Google, there are 1,527,408 people in the U.S. named Jennifer.
There are 661,933 people in the U.S. with the first name Amanda.
Do you see my point. A first name is not much to get excited about. A lot of people have the same first names, but if you attach a last name to that first name, you may still have a few thousand in the country, but it would be enough to prompt asking for further details.