There has. And there is.
In the 2008 run-up, farmers could see the difference between what they got and what was being shown in the close-in futures prices, that futures were bid up over the physical by increasing margins from “reality.”
Prices of food going up due to temporary disruptions (usually weather related, or government related (the stupid policy of burning corn for fuel)) is usually temporary as bubbles could burst as soon as the next harvest anywhere in the world.
Gold and silver are different in that they are hard to find, and it sometimes takes years to gain required permits. Also, the whole world is still under-invested in the precious metals, including central banks. When everybody from the bus boy to the bus boy’s grandmother is invested in gold and silver, I will say there is a definite bubble.