In this sentence ‘das’ is used by itself as a kind of general pointing word. Unlike when it's used as the neuter singular of ‘der’ it doesn't imply anything about the gender or number of whatever it points to. You can use it to point to people, things and even situations.
You need to know that it has nothing to do with the letter "b". It's a special kind of 's', so you should find it under 's'. I don't own a Samsung, but on an iPhone you just hold down the s-key to get access to the special s-letters.