[General Questions and Answers] curiositykilledthecat:
The Problem:

Sometime last week, several--but not all--of my text messages disappeared from both Google Hangouts and my native SMS app. Only recent texts went missing, while past messages from those same people were visible in the Contact History. I noticed for two reasons: 1) my incoming messages after last Monday all were basically new threads and the previous texts with those individuals/groups were gone, and 2) I needed to keep a record of a particular thread with my ex who became abusive in the case that I would need to file a restraining order. He is bright, but borderline which means he's unstable. I am anxious about having lost those texts with him and also insatiably curious, which is why I'm posting here.

Sidenote: Yes, I have heard of SMS Backup & Restore. No, I did not use it before. Yes, I plan to use it in the future.

My Phone Details:

Samsung Galaxy S3 (SGH-T999L)

Android version 4.3

Baseband version T999LUVUBNF4

Sidenote: I know missing texts is a known issue with this phone, so if that is what you think it is after reading this, please tell me. However, it's bothersome to me because all threads before 3/23 disappeared from my SMS app, BUT I can still see *some* (but not all!) texts by looking through my contact history. Also bothersome is that on 3/20, I told my ex (by text) that if he did not stop contacting me, I would file a restraining order. Of course this mysterious loss of data could be completely coincidental, too.

What I've Tried So Far

1. I tried to use Dr.Fone software to find the lost messages. It got stuck at the "Analyzing Device" screen, so no luck there.

2. Yesterday, I rooted my phone after poring over this website for several hours. I used CF Autoroot. Although I was unsuccessful at using adb commands on both my phone (Terminal Emulator) and computer (SDK), I was able to navigate the root directories using ROM Toolbox Pro (Hallelujah! That process was driving me crazy!).

3. I looked at all the "mmssms.db" databases (/databases/com.android.providers.telephony/mmssms.db) - no luck. It only contained the recent messages that are visible in the SMS app.

4. I discovered that I could see older text messages by looking through the Contact History (View Contact > History). Many threads were deleted all the way back to 2014, but 1 thread still had texts from 3/22/15. So, I went on the hunt and discovered "logs.db" (/databases/com.sec.android.provider.logsprovider/logs.db).

5. In logs.db, I could see up to 1000 rows with the names of people, including those people whose threads were deleted. Their names and numbers are all present and accounted for, but when I view the M_Content column, I see a bunch of blank spaces where text content should be, all the way back until April of 2014 (with the exception of the thread with 2 texts on 3/22/15).

Other Strange Happenings

This could be selective memory, but in the last week my phone has been acting very strangely, turning off spontaneously, even when charged, and getting lots of error messages (Sorry, X App must close).

The Chicken Or The Egg

What do you think? Is my phone glitching and therefore I lost the data, or did I lose the data, perhaps by some nefarious means, and therefore my phone is glitching? Does this sound like a typical data loss situation to you?

Final Caveats

Please use layman's terms. I am not an expert by any stretch, so the more jargon used to advise, the more hours I will spend trying to discern what you are trying to tell me.

Thank you in advance for your help.