Quick answer
What you need to know
The key is hidden among the potatoes. Keep the collect, peel and sell loop moving, watch the processed area, and take the key to the vault as soon as it appears.
Expect a late find
The two reviewed Roblox runs revealed the key at different points. Do not rely on a fixed potato count or location.
Keep every station productive
Collect in useful batches, process them, sell, then reinvest in the slowest part of the route.
Leave for the vault immediately
The hidden key is the objective, not an empty mountain. Once it appears, stop grinding and escape.