Hi Gabriella,
Glad you've having a great time (though I wouldn't generally recommend actually stopping when you're flagged down there...)
I'm just passing through here, but briefly:
The trouble with NPF being asserted because someone thinks a statement that hasn't been made by a theist is being implied, is that the implied part is no different from guessing, unless the theist subsequently confirms that they were trying to imply a true for everyone argument because their claim can't be disproved.
No, it's stronger than that. The NPF is sometimes used to answer the question, "what's your evidence for "God"?". That is, in these cases the person saying, "you can't disprove it" is so far as they're concerned providing evidence
for their god.
As a separate matter, even if no-one had done that the NPF would still be a bad argument and so shouldn't be attempted regardless of the intent of the person essaying it.