Eleven days after the mother of “Today” show host Savannah Guthrie vanished from her home in the foothills outside Tucson, Arizona, investigators had yet to identify a suspect or even a person of interest Wednesday. What seemed like a major break Tuesday — when authorities detained a person for questioning — fizzled when the man was released hours later. The detainment followed another potential break earlier in the day when investigators released video footage showing a masked and apparently armed man at Nancy Guthrie ’s doorstep the night of her disappearance.