I've run many rounds, that were hiding in my jeans pockets, through the washing machine.
And they've all fired just fine.
And that has to be more of a water threat than high humidity.
I'd bet this squib was caused by no or low powder, as the few that I've experienced were.
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”