I thought they couldn’t do that. The Gov. has the option to replace them?
No, no governor can replace a congressman. Whenever a congressman resigns or dies, at the beginning of his or her term, the governor, of that state, must choose a date for a special election. In 2008, ex-Rep. Hastert resigned, and a special election was held, in Illinois. Gov. Jindal, of Louisiana, resigned his congressional seat, and his district held a special election.