Couldn't find an attributory quote near to the one you described, which also happened to link to either of the authors mentioned.
However, it did come to remind me of a certain film dialogue that pertains;
Paul Edgecomb (The Green Mile) - Memorable quotes
Either way, that's what I'll leave you with, in addition to telling you to just use the quote you described as your own, and if need be, cite it as an author integral to your spirit, but the name was discarded/forgotten long ago, if only because the message of which they spoke was more powerful than their name/fame. If the author comes up by chance in the future, though, seize it to your committed memory, so that nagging feeling in the back of one's head can finally be let free.