It isn't really possible for something like that to go unnoticed. Any time anyone at all makes a big transaction, there are a bunch of posts about it on Reddit

It isn't really possible for something like that to go unnoticed. Any time anyone at all makes a big transaction, there are a bunch of posts about it on Reddit and Twitter, because everyone is watching all the time, and Bitcoin is easily auditable. But! There are some coins that focus more on privacy, such as ZCash. And those coins are indeed vulnerable yo this situation. Maybe there is a secret transaction, that has already happened that massively increases supply. The coins can't be audited, so they are there. This problem does not exist in auditable Blockchains though.