As mentioned by nannymo upthread:
"'He usually talks to my daddy on the way to work,' said sister Gena Arms.
Walter Arms says the day of his son's disappearance he did talk to Lee, 'And he told me dad I love you and I told him the same thing.'
Once Arms reached Interstate 10, he ended the call with his father,
'He said daddy I'm at I-10, I'll talk to you tomorrow, I love you and that was it,' Gena Arms went on to say."
So the thought had crossed my mind that maybe Lee had made plans to meet up with someone specifically at the spot where his vehicle was found, as it's just a couple of miles south of where I-10 intersects with Loop 1604. I also noticed that his wife remained quiet throughout the ordeal, with his side of the family doing most of the talking, but that may very well have been because she simply was overwhelmed by what was happening. Additionally, it may be worthwhile to point out there was confusion over what he was wearing the day of his appearance prior to the release of surveillance fidel footage; looking back, perhaps he had taken changes of clothes with him. If he planned to fake his own disappearance, he did a pretty darn good job.
I also think it is still possible Lee was involved in some sort of accident or altercation, resulting in a head injury, and was maybe taken to a hospital by a good Samaritan; since he had left all of his personal items in his car, perhaps it took the hospital staff a while to identify him and get in touch with LE.
In any case, the best possible outcome, IMO. Best wishes to Lee, his wife and their three children.