Ummm, I'm no lawyer - but the issue is going to be whether it came from Cousins' phone or a phone that somebody can prove Cousins' controlled.
If the text came from Cousins' phone, he's probably not going to play the, "How do you know that's my junk? I might have lots of random junk shots on my phone. Did you think of that?" card. And it's probably not a good defense anyhow.
I don't get this issue but it comes up, Oden, Ellis, George Hill, ect. This person is going to get an attorney, who will be able to prove pretty easily whether Counsins used the phone. Pretty simple.
But you are right, I don't think there will be a lineup to see if it's Cousins' junk.