Bible corruption is a common argument from various different religions, but most arguments in its favor are so utterly destitute, even the ones who make those arguments will admit they're ridiculously weak, and that the Bible we have today is pretty much identical to the original. There are no meaningful variants (i.e. any which, if we didn't know which variant was correct, would alter the faith), there is no missing content, even the stuff that was apparently added is fairly easy to deal with. It's called "textual criticism", and with such a wealth of material to draw from, any claim that the Bible has been corrupted is dead on arrival.
But when people desperately want to believe a conclusion, no matter how blatantly false that conclusion is, they are all but guaranteed to find an argument for it. Enter Jeremiah 8:8, a verse which, allegedly, says the Bible is corrupted. Now, before we even read the verse, does anyone else notice a few glaring errors? From a Theistic perspective, if this is God saying "you corrupted the Bible", was there not plenty of time for Him to restore what was lost? We see later in this same book, God says to Jeremiah "Take yet another scroll, and write on it all the former words that were in the first scroll which Jehoiakim the king of Judah has burned." (Jeremiah 36:28), so obviously the omniscient and omnipotent God, who had a prophet sitting right there ready to obey Him, would have been more than capable of of restoring a corrupt book.
Even if you're not a Theist, or believe in a weak and petty god who can't defend its words against man, you have to admit, especially if you believe the rest of the Bible after this is made up, that whoever wrote the rest of the Bible would have claimed God restored what was lost according to Jeremiah 8:8. Furthermore, if people are capable of corrupting the Scriptures, they're not going to leave in "by the way, we corrupted the Bible", are they? So in other words, even before we read the verse, we see that this argument is dead on arrival.
With the elephant in the room satisfied, let's read the actual verse: "“How can you say, ‘We are wise, And the law of the Lord is with us’? Look, the false pen of the scribe certainly works falsehood." You can see why liars would have chosen this verse to support Bible corruption, but what the studious observer will see is what these same liars have cut off: "The wise men are ashamed, They are dismayed and taken. Behold, they have rejected the word of the Lord; So what wisdom do they have?" (v9, emphasis mine).
In other words, the pattern described in Jeremiah 8:8-9 is the same as can be seen today. It's not that the word of God was not actually present, but that people rejected it, and forged it. Even if there were somehow scribes that had managed to produce scores of fake Bibles, that still wouldn't have touched the original.
We see, then, how Jeremiah 8:8 does not even come close to defending Bible corruption. It says there were corrupt scribes and other heretics floating around, it certainly doesn't say the Bible was corrupted.