Well they can get dirty. Mine worked on and off when it was dirty. After I cleaned it with mass air flow cleaner it worked fine. If you can't find the line, it may not be there. I don't think I have a picture of one branching off of the tranny.
Are you talking about a little silver nipple off of the tranny pointing upward? Located kinda by the passenger wheel well?

Edit:
Found a picture of it.


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