I too am amazed at the toughness of orchids . I repotted one a few months ago , no roots to speak of left on it . To my amazement , it has grown at least 4 new roots and leaves are doing very well .
Never give up , even if there is no green left.
I am surprised with the people I talk to also . When they buy an orchid in bloom , and when they have finished flowering , they will throw them out . What's up with that . They are totally missing something special .