I don’t believe that is what he is saying happened. He was in the middle of typing a message in the text messaging app and he opened another app/task, in this case Safari, (the copy and past bit is irrelevant) and when he toggled back to his text msg. app the message he was typing in the text message field had totally disappeared... the text field suddenly went blank. He lost his response or new unfinished message simply because he opened a new task or app.
I would also venture to say that he could probably still see the content he had been typing into the text field while the open text message was showing in his multitasking screen and when he selected the text app in order to toggle back to it to finish his message, all of the content he had typed (and had still been able to see was there right before he toggled back to it) had gone blank.
This also happens to me but only on occasion. Sometimes the content is still displayed after I toggle back, other times it totally disappears as if I hadnt just spent 20 minutes trying to “thumb” a text message to someone. It’s frustrating and he (and I) would love to how to prevent this from happening and most importantly, how to recover the deleted and of course, Un-sent message content. (I can just use Control-Z on a computer. There MUST be something built in to this technology that is similar. If not, there should be but that’s beside the point.