Unfortunately oyster pearls don't tend to have much value, especially if they've been cooked. It's a common misconception that pearls come from edible oysters. While any bivalve can produce a pearl, those that come from the mollusk family Pteriidae produce the nacreous, valuable pearls. Edible oysters are from the family Ostreidae, and pearls they produce are non-nacreous and rarely carry much value.
Aside from the technical aspects of it, finding a natural pearl, regardless of quality and/or value is a very, very rare feat