Maybe this can help:
-Go to google and type playstation, click on what you find to go to the main site.
-Look for Support and contact Sony about this mistaken e-mail address from the guy.
If you get nothing back...
-There should be a sign in icon on top right, click there.
-Enter your e-mail and hit Forgot Password.
-When you get the password e-mail, login to his account and see if you can somehow message him, if not you might still be able to message people in his friend list.
-If you're fully ignored, go to his account and delete his credit card detail (so you're not stealing but by changing things he'll notice something's wrong).
-If everyone acts like an A-hole, get his card detail and buy me Super SideKicks from the PSN store
.