Closed Airspace

I suspect this is your explanation:

Now that makes sense. Especially since after I went VFR, the
controller gave me a time at which to contact Seymour Approach if I
lost radio contact with him before I got a hand-off. He came back
later and said there was a change of plan, and that another controller
had agreed to work me VFR to the south, so I never had to rely on the
timed freq change, but it does rather fit with this story.