I think it’s more likely to be a broken-off drill bit, there would be no need for anyone to try screwing anything in the hole. If it is a drill bit, it may pull out if you can grip it with pliers. If it’s hidden by the bridge plate, you can drill round it enough to expose it enough to grab it firmly to remove.
Then drill out big enough to glue in a hardwood plug and then re-drill for the bridge screw.