This account mentions that Cherita, who was 20, was heading to a local bar with a friend for drinks:
Cherita Janice Thomas – The Charley Project
Michigan, however, had raised its legal drinking age back to 21 in 1978 after an attempt in the earlier '70s to have it be 18.
So, call me silly, but is it even remotely possible that Cherita's body might have been found years ago, but with a fake ID, and that threw off LE in connecting it to the real person? Stranger things have happened, IMO...