When you stake your tokens, they are no longer in your wallet. See this MetaMask Knowledge Base article which breaks it down as "It’s helpful to think of staking as similar to putting your tokens in a savings account, or as depositing them with a third party. On a technical level, when you stake a cryptoasset you are generally committing that asset to be controlled by a smart contract, in exchange for something, usually an alternative token of some kind. " The article dives deeper.
To get it back in your wallet, you’d have to unlock them/no longer stake them. To see the balance staked, you’d just utilize the Polygon staking dashboard to see/track your balance.
Here is more FAQ if it helps: