Surely any adult with half a brain would read that and understand the intention? they wouldn't just head off to start digging for gold...or are people really that fucking dumb I think I already know the answer to this?
Anyone else old enough to remember a lovely children's book/puzzle, there were clues in the illustrations which would lead the first person to correctly solve it to a silver hare concealed somewhere? It caused chaos. The author had clearly stated that the silver hare wasn't hidden on private property, or buried anywhere that was a scheduled ancient monument. But crazed treasure hunters were breaking into places like Stonehenge to dig around etc. His name was Kit something... it'll come to me.
Cadbury haven't been terribly bright with their promotions lately. Creme eggs may not be as tasty as they used to be but I do occasionally want one, their promotion of offering a cash prize for a white creme egg means every single one on the shelves has been haphazardly peeled open and resealed with likely multiple strangers raking their fingers across the chocolate in the process.
I've just had a look at the Cadbury's web advert. It's dreadful - there is absolutely no mention of the fact that metal detecting and digging on virtually all the sites mentioned is extremely illegal as well as utterly immoral (puts archaeologist hat back on despite having not wielded a trowel in anger for 20 years...)
That white cadbury's creme egg thing sounds bonkers too. I've been boycotting Cadbury's anyway for a couple of years now but that's even more grim than usual.