Messages should be shown as seen when persin recieves and open it.

[1988chyna]

If someone opens your text message it should say seen when the person who sent it goes back in looks to make sure the person gotit.

 

[Rukbat]

Some texting apps have "read receipts" that will show you that the text was read - if the person receiving it has a texting app that sends them. And if the person actually reads them. No software can tell if someone is reading a text or just has it up on the screen and is ignoring it. If you need to know that a message was received, word it so the person receiving it will know to text you back.