I mean gold is very dull, almost invisible and traditionally not very easy to spot against a green wall because yellow is such a similar colour and doesn’t contrast with green at all.
And even if it were, humans are notably not at all prone to shouting ooh sparkly! whenever they see shiny things.
I think we probably have a game design error commonly referred to as PEBCAC (final C refers to controller in this instance, I really don’t know why. Some programming thing I guess).
If you truly still can’t spot the hugely sparkly gold in the wall please tell me you looked at the walls or at least up then I’ll help out via Picture in Picture
Edit. Did you have the torch off? Were you In total darkness?