JJust as there are some people that don't seem to have a proof of their existence, so it is for companies on the blockchain network. Most times, these types of exchange platforms tends to be scam as they would delete any trace of their existence so as to try to cover up. They just don't seem to know the fact that there are still some people who might have used it before and can claim its existence one time in life.
An example of an exchange platform that tried covering their existence is the AjuBit exchange platform. AjuBit exchange platform is one that I don't even know its country of origination. Their website don't even exist and there seem to be no social media accounts attached to the exchange platform.
Among all these, the fact that some traders have once used the exchange platform validates the fact that AjuBit exchange platform has once existed.