Frost me,
That's a bummer. How large a pearl is it? Can you see if the knot is closer to one end? I'd try soaking the pearl overnight in water, to help soften the thread. Then try using a reamer to get the threads out. OR take a sewing straight pin and bend the very tip into a sort of hook, or at least to the side to pull the fibers out a little at a time. It's a fiddly process, for sure, and no guarantee, but these are a couple of things I've done. Do you think there is glue in there also? If there is glue, the hot water trick will help loosen the glue. Please let us know how it goes.