Glad your actions kept you out of harms way!!
Others:
These events require situational response; so every collision any particular driver can see "unfolding" in front of them will require very specific response. I think that Mr Phelps judged this one correctly.
I know someone personally (a truck camper that once frequented this Forum) who had a VERY similar situation; however, they had stopped completely, and were sandwiched by slow traffic in front. The "car" that merged into their lane crashed head on into their F250; remarkably, everyone survived. This one could have turned out for the worse if it weren't for their (limited by situation) evasive action (situational).
On edit: while driving to Florida this past winter, "we" were shocked by the quantity of drivers who talk on hand-held cell phones on I95. Additionally, how many hold theur cell phones near the steering wheel, and text. Virtually every State we drove through had many, many offenders. Are there no laws against this in the US? Locally here in Quebec, I have only seen appx 3 drivers doing this over the past perhaps 5 or 6 years. In the US, we counted in the 6 or 7 dozen over a period of 2.4 days on the I95 through appx 9 States.
For alert and experienced drivers (like me/us), it is very easy to spot drivers who fiddle with their cell phones while underway.