Text is not in Message folder but can search for it

[mengoi]

A friend borrowed my iPhone 4s and texted someone.
I want to delete those texts on my device and
I don't see his messages in Messages folder but I could search for his message on the search page of iPhone
The icon on the left of search result showed that it's from Message folder
When I clicked on the search result, I was brought to Message folder but didn't see that message.
If I searched for my messages which are in Messages folder, I would be brought to that message.
I turned on airplane mode and tried again. I was able to search for my friend's texts but I was unable to locate where his texts are.
Any one can teach me how to find texts?
Thanks,
An

 

[jgalan14]

Sync your phone with iTunes, the iPhone deletes it from your bien but SMSs are still on system memory the only way that they are completely deleted is when you sync