As you say, the odds of this happening are very close to zero. But suppose for a minute that this was possible. Did you learn anything? Do you really have a discovery? Was this done using a novel method or applying something that already exists? If you give this to somebody else, should they believe it works? Is this result even understandable by human beings? You'd need to answer so many questions that in the end even this would NOT be a discovery by the machine but by yourself.
Scientists discover things that I don't understand every day.
A sufficiently advanced discovery in, say, mathematics can only be understood by other mathematicians. Does that make it less of a discovery? So what's wrong if a machine discovers something that can only be analysed and proved by other machines?
The mathematicians understand the discovery, so what's the problem? With "AI", nobody understands it. If you ask, the AI may say it understands the results, but it is probably lying.