how in the **** can a person delete the text message they sent me from my iphone ??

General text messages cannot be deleted remotely. However, some apps allow deleting messages in such a way, the default messages app does not.

What app?

Don't you know what app you're using for text messaging?

No one can delete message in the built in messages app from your phone.

I know WhatsApp allows remote deleting. Not sure what other apps may/may not.

Signal, WhatsApp, Messenger, and some others all permit remote-delete messages.

Apple Messages does not implement remote-delete messaging.

But we do not know which app you are using until you tell us.

As for one potential option: Take a screenshot on your iPhone - Apple Support