>I wanted to find a particular message. Since I didn't remember exactly the setting, I decided to go using a complex route through my friend (I remember she got the answer I wanted).
>
>So I tried to search by her first name "Mariam" and it didn't return her ID. Only using few first letters of her last name I was able to find her.
>
>Why the first name search didn't bring her?

As confirmed by Nicholas, yes, the search on the first name field has been removed as it was too generic. John Koziol mentioned about that a while ago. When the change was done, I included a search in the email field.