If I were in your shoes I'd ring the insurance co that you are with pretending to be a new client contemplating talking out insurance with them and ask if they'd cover a pin and what you'd have to do to achieve this. Ask them to highlight the sections and wording in the policy that would be relevant, get as much info as you can while they think you are a potential client.
You're then in the best position from the point of view of information to make a claim.
On the pin itself I wonder if you got to it fairly quickly and it didn't sit around wet for too long, it might be ok after drying out? I hope so for your sake.
