As you probably know, blockchain transactions are irreversible. If you mistakenly sent funds to a validator rather than voting for them, only the validator can return them.

You will need to contact the validator and ask them to refund the transaction. If you reach out to them, Polkadot validators will likely return your funds because the Polkadot ecosystem is designed to incentivize good behavior. This tends to result in more votes and trust from the community and, therefore, more influence and financial rewards. The opposite is true for bad behavior.

Polkadot validators can set their identity and provide contact information on-chain. Validators with an on-chain identity will have their name and not account address displayed on the Staking Dashboard or Polkadot-JS UI. To see their contact information, you can look them up on a block explorer or click on the validator's name in the Staking section of Polkadot-JS UI. Contact information may include the validator's Twitter account, email, website, and more:

On Polkadot-JS UI, validators that verified their identity with a registrar are marked by a green icon (with a checkmark or chain) next to their name. Validators with a grey icon have set an on-chain identity, but their information has not been verified. However, it is reasonable to expect the information to be correct in both cases. The Staking Dashboard does not differentiate between verified and unverified identities.

However, not all validators have set their on-chain identity on Polkadot. If the validator that received your funds does not have any on-chain contact information, it may not be possible to contact them. Since Polkadot is a decentralized and permissionless network, there is no way to make the validator return your funds.

Be sure to share your experience in the Polkadot community on Element, Discord, or Twitter, so the whole community can continue learning which validators are the most trustworthy.