I meant to gather more examples before posting this question, but here we go. These are some lines out of various Ghibli movies I saw last weekend.
わからないは - when asked to take a guess about something いないは - after looking for someone in a specific place
I realize this is casual and may not be strictly grammatically correct. Still I wonder what's the reasoning behind these type of sentences. It's not difficult to understand what they mean, but why は? How would a native speaker justify the particle? And if someone can tie it to some formally correct version of the sentences that would be great!