It baffles me that transport operators (mainly airports but why not Eurostar too?) don’t offer a “we’ll courier it home for you” service. instead of confiscating private property – and needless to say not offering any compensation – they would provide a service, turn a hostile situation into a less hostile one and quite probably also make a profit.
I did once try to board an aeroplane at a small airport in Scotland forgetting I had some scissors in my hand luggage. The scanner found them … and then offered to post them to any UK address for me. She even had a supply of envelopes and padded bags by the scanner. Sadly such creative thinking seems to be completely beyond the automatons who run most security desks, for whom showing initiative, helping customers and thinking laterally all seem to be “not part of the job description”.