There have actually been three "13th Amendment's":
The first was the "Titles & Nobility" Amendment, which would have made it illegal to accept money or title from any foreign head of state, without the express permission of Congress.
The second was in 1861. In an effort to stop the South from seceding, there was a proposed amendment that would have prohibited any future amendment or law from abolishing slavery.
Then there was the 13th Amendment that made it into the Constitution, abolishing slavery.