It appears as if a hidden field's NAME value starts with a number, the plugin doesn't render the input tag. For example:
[hidden 00NA0000003xV2w "Homepage Contact"]
I tried putting a letter at the start and it works:
[hidden A00NA0000003xV2w "Homepage Contact"]
I'm trying to use this with Saleforce and they have 2 hidden fields whose name starts with numbers. Help!