I lost two Boykins, one to theft and one that must have jumped off our pier when the lake had frozen over. (a rare occurance here in Alabama) My several great grandmother was Amelia Boykin. Her nephew Lemuel (Whit) Boykin is given credit for starting the breed. Hope your search is successful, I feel your pain.
Many don't know that Boykin Spaniels are a South Carolina breed that originated just up the road from here at Boykin, SC (a few miles East of Camden, SC) I'm going back to the area tomorrow and call a few vets in the area. You may want to run an ad in the lost & found section of The State, The West Columbia Journal and the Carolina Trader papers.
Best Wishes that you find her......George