I did the same thing with a Nancy Silverton starter but with a much larger amount--enough to fill up an entire baking tray. After breaking up the dried "sheet" into smaller pieces and putting them into a plastic storage bag, I stored the bag in my pantry where I proceeded to forget about it. More than a year later, I stumbled across the bag again and decided, purely out of curiosity, to see if I could rejuvenate the starter. To my surprise, it worked. I don't know whether in the process of drying the starter originally or in the process of rejuvenating the starter later I picked up natural yeast all over again, but I ended up with a viable starter. I also sent a piece of the dried starter to a brother in Massachusetts and he was also able to rejuvenate the piece I sent him.
I believe fellow member davtrent also reported on a similar experience in rejuvenating a starter from a dry format.