Chosen Solution

How can I recover a deleted message that was deleted today, 4/12/17 by mistake

Not totally possible if you didn’t happen to have a backup performed after the message came through, but before you deleted the message. If you did have that backup you can restore from iCloud or iTunes.

As Matt Zieminski says, if you have backed up your iPhone before, you can try restore. But this might replace all existing data and the process is to some extent complicated for new users and time-consuming. If there is no backup, the only way to retrieve deleted messages is using an iPhone message recovery tools, and you should avoid using your iPhone to prevent the deleted data been overwritten so no tools can recover them. Try PhoneResuce, Dr.fone, Primo iPhone Data Recovery, great tools to retrieve iPhone messages. Here is a guide: https://www.primosync.com/support/how-to

It’s very likely to delete some important old messages by accident, regretfully. Actually, after you remove a message from iPhone, the message doesn’t actually get deleted. You are most likely to recover deleted text messages if you act quickly right after accidentally deleted them. That’s because those texts won’t actually lost until they are overwritten by new files.