ON CHRISTMAS DAY 1987, Heiderose Ursula McGuire went to work at the Circle K convenience store in Denver, Colorado and was never seen alive again. At the time, her brother told her the job was not safe but the 18-year-old beauty and recent high school grad was undeterred. But just in case, she had found another day job and studying accounting at a local college. Her family said she was trusting According to the Denver Post, on Dec. 23, 1987, two days before her last day at the Circle K, 