Did you check your Junk emails? My iPhone decides which emails are junk and which are not.
Click on the Mail button, then click on the back button in the upper left corner. You should see two headings. One is Mailboxes and the other is accounts. Under "accounts", click on the email address you want to look at. It should open several categories. Look in Junk, Trash, or any others you think the emails might be in.
That's as far as I can take you. If they are not there, maybe someone else can help.