I did not add it to the newthread template as it is automatically included in newthreads.
Custom Thread Fields Wrote:The key through which this field is accessed through. Should be kept to alphanumeric characters, underscores (_) and hypens (-) only. Note that only inputs for this field on newthread/editpost are automatically added for you; forumdisplay/showthread etc templates aren't affected, so you will need to make changes to the relevant templates for this to be useful. Use {$GLOBALS['threadfields']['key']} in templates to reference this field (this is slightly different for file inputs - more info given below if you choose to make a file input).
Its not using a separate template in the global templates, but the default template. I have not yet tried with {$tfinputrow['key']}