I am amazed at the quality of cell coverage in certain areas of GSMNP (thru Verizon).
I was in the Deep Creek area and Newton Bald last week...
4G coverage on Newton Bald and Campsite 51
3G coverage at Campsite 46
1X coverage at Campsite 60
As for the OPs encounter, I don't specifically recall a similar encounter. But agree with others that say there's nothing more the OP should have done (other than quit worrying about it and "move on" 3 seconds after it happened).
It sort of reminds me of Hanlon's razor "Never attribute to malice that which is adequately explained by stupidity." That razor isn't exactly a perfect fit for this situation, but similar.