You do know the Tiennamen square is the literal most famous place in China right? It's the place where there is this super famous building that is one of the country's symbol and that almost every content about China ever can't help but have at least one picture of.

So saying that the name of the place is censored in China is completely ridiculous.

As pointed out by others, the event that you are referring to is known in China as the june 4th incident so yes, of course if you type Tiennamen in the search bar you won't find it, when you look up something on a non-english website maybe try to look up how the thing you're looking for is called in the site's language instead of assuming it's called the same way in english you westernbrained monkey.