Umm, you mean that
(including for example lucky pebbles)
doesn't work!? My seven year old daughter has been picking up a stone most everywhere we land, and we've been getting home just fine. She found a very pretty piece of quartz today. Soon I will have flown home the start a very pretty driveway!
On the other hand if pebbles work, I guess water must be lucky too, 'cause when I take her in the amphib, she just comes home a bit wet, but no pebble!