I believe there is no （ ）thing

因为前面是 no
no = not a/not any
no such thing = not such a thing

thing是抽象的东西,不能用a

因为thing前没有形容词
such+a+adj.+sth=so+adj.+a+sth

这里 no such thing
not such a ___ thing 只能在有其它修饰词或指很明确的事情/物体时用，如
That's not such a good painting.
那幅画不怎么样嘛。