I believe this issue can be replicated by anyone who owns an iPhone . From what I read online the messaging app and spotlight on the iPhone seems to only index some messages for a period of time.
Find someone you text regularly and go back 5 months. Find a key word or phrase in that time frame and then search for it with both spotlight and the Messages app on your iPhone. My guess is you won't find it. Try this with a few other contacts and see. Some times it works and other times it doesn't. Both Spotlight and the iPhones messaging App may even give you different results. Then see if you click on the result if it takes you to actual message and highlights it.
What I cannot figure out is if this is done deliberately for a reason that I can't think of or its a bug.
Part of me thinks it's a bug since iOS 7 as I've found a few posts online about it with temporary fixes of all sorts. However the problem comes crawling back. Some people have even said this happens every time they do an iOS update. Any messages prior to the update are no longer searchable but not for me. I'm able to find some message prior to iOS 9.2 but not all of them.
Some fixes I've read have been to do a complete reset, change the language of the phone, turn Spotlight off and on and delete network settings. Not sure how the last one would work but it did for one person. Regardless though it's an odd issue which always come back for people.
Find someone you text regularly and go back 5 months. Find a key word or phrase in that time frame and then search for it with both spotlight and the Messages app on your iPhone. My guess is you won't find it. Try this with a few other contacts and see. Some times it works and other times it doesn't. Both Spotlight and the iPhones messaging App may even give you different results. Then see if you click on the result if it takes you to actual message and highlights it.
What I cannot figure out is if this is done deliberately for a reason that I can't think of or its a bug.
Part of me thinks it's a bug since iOS 7 as I've found a few posts online about it with temporary fixes of all sorts. However the problem comes crawling back. Some people have even said this happens every time they do an iOS update. Any messages prior to the update are no longer searchable but not for me. I'm able to find some message prior to iOS 9.2 but not all of them.
Some fixes I've read have been to do a complete reset, change the language of the phone, turn Spotlight off and on and delete network settings. Not sure how the last one would work but it did for one person. Regardless though it's an odd issue which always come back for people.