My tokens were stolen / sent in an unauthorized transaction
We're sorry to hear this - unfortunately like on all blockchains, on Theta the transactions are irreversible. We do not have any centralized control over addresses or tokens and cannot move them without the private key to that address. The only way someone can access a Theta Wallet is via the addresses' private information (i.e. the private key, 12-word mnemonic phrase, or encrypted keystore), so the most common cause is that your private info was compromised either by malware on your device or a phishing attempt/site.
If the scammer moves the tokens to an exchange wallet, it's possible you could get the exchange to hold the tokens when they are sent there. While there is no list of exchange addresses and they change frequently, they can often be identified by a large balance and frequent transactions (ex. here is one of Binance's Theta wallets: https://explorer.thetatoken.org/account/0xe357f83708eaeddee700afe97ebe6a7ed27de555). Often using a web search on the address will identify which exchange it is. You can then contact that exchange and see if there is anything they can do to freeze the scammer's account at the exchange to recover tokens, though it is at the discretion of the exchange.