Insurance claim

Advice please. Buyer bought three porcelain items from me.One item arrived with a hairline crack.Total cost was $75. I took extra insurance cover of $100 in case of loss or damage in transit. Buyer says they cannot claim as they have disposed of the packaging, but is now asking me to refund $25. This infers that the fault is mine.I pack very carefully as my record shows, I handled the items when taking the photos and when packing and did not see any damage or I would not have posted.

      What action should I take? I want to do the right thing.

      I appreciate and thank all members for advice given and time taken to answer my query.Patricia.