Thank you for your advice. It sounds like you think that I think my phone is alive and making decisions on it's own, lol. When the device did not act as expected, I did check the settings. I have minimal information stored on iCloud as their track record for keeping information secure is not good at all. I choose to back up my iPhone to my PC.
To the issue at hand: as mentioned, I thought I saw a blue text bubble while groggily texting my friend (an iPhone user) early one morning. I hit send and fell back to sleep. Some days later when I noticed that I hadn't received a reply, I checked to see what was going on. The message wasn't there at all.
A few days ago, the same thing happened. I opened the Message app and selected the conversation. I tapped to type and a blue text bubble appeared. I proceeded to compose my message and hit send. I saw the blue progress bar at the top of the screen stall near the end hanging for a few seconds, then the message disappears. I guess, because I have chosen not to use iMessage, it dropped the message entirely. It would have been nice to receive a popup informing me of this and give me the option of sending the message via SMS. In fact, it shouldn't have brought up the blue iMessage bubble in the first place! This part is not a carrier issue.
The problem with the same contact with 2 conversation threads may be SMS related. However, I tend to think that the Message app sees the contact as 2 different people while the Contacts app shows it as the same person. Updating to iOS 13.3.1...
