How can I retrieve all text messages sent and received from a particular person?

If they are in a backup file you still have, you can restore the device from that backup. Otherwise there is no way. Carriers do not keep your SMS/MMS messages nor does Apple keep your iMessages. All texting systems purge messages as soon as they are successfully delivered.

Unless you keep copies or backups yourself, there simply is nowhere to retrieve texts from.

I agree with Michael Black's response, and very likely that is the solution to your issue.

But there is a small chance your question really means something else - in particular:

"I have many (hundreds?) texts on my iPhone currently. How do I find those sent and received from a particular person so I can ferret those out from the rest of the messages on my iPhone?"

In the (unlikely) event this is what you mean, then you may use the search field in the Messages app to enter this particular person's name.

It doesn't.

I have just bought a program called iExplorer that promises to retrieve and organize all kept messages sent and received.

You should be calling them and asking about the promises they make.

I notice that the iExplorer app in the App Store both has many awful reviews and has not been updated in one year.

bankolefromellicott wrote:

iExplorer is used by Apple.

No, it is not.

bankolefromellicott wrote:

ouch...did I touch a nerve? iExplorer is used by Apple.

It is not.

In your original ppost you did not mention that you had set the phone to keep them forever, so I assumed they were not on the phone. Of course, if you've kept them in the phone, they should be available. If you've deleted them, then not.

Either I don't understand what you're trying to do, or you're not explaining your situation fully. If you've kept messages forever on the phone, then why do you need to "retrieve" them?

I'all say again though, that unless you have kept the messages somewhere (your phone itself, your backup, copies on your computer - somewhere you have actively archived or backed up messages) they are not retrievable. Carriers and Apple purge messages from their servers once delivered. If unable to deliver, Apple keeps message queued for up to 30 days and then purges them, while most carriers will only keep undelivered messages queued for a few days at most.

bankolefromellicott wrote:

yes they are set at "forever" so they should be somewhere on the iPhone. Not so?

Not necessarily if you've changed devices at times. Your previous device's messages would need to have been migrated with a restore from backup. Otherwise, the new device started off from nothing.

You should probably ask iExplorer rather than Apple.

Apple does not retrieve messages for anyone. People are responsible for their own content of their own devices. Apple offers no data retrieval services of any kind, for any device.