If you just make a mistake in the account number and hopefully the account number isn't real at that bank then the money will be returned to you.
If you send the money to the wrong checking account number and it happens to be someone's checking account then good luck getting it back.
You'd have to prove that you sent it to the wrong account number and hopefully the person would cooperate and send you the money back.
If not you'd have to contact the law enforcement to get it back. But any honest non criminal person would just send it back to you to avoid any legal trouble.