Common sense says an oversize pebble may not be as it seems..That's probably why it was confiscated.
Palma can be worse that that - My wide bought a souvenirs that contained a liquid - Not only was it took, she suffered verbals..A male gave it her back after close scrutiny and realising it was bought in Majorca,
For some reason I always seem to get frisked, or my bag searched at BLK - Who cares?..Better a little inconvenience that being blown out of the sky.
I would be more worried if the security was lax.