Have you discovered some token were disappearing within the market at this period. Such as Bitboost just suddenly disappeared away from market without prior awareness. Should that be? Is that not a cheat?
I think you have misused the term "disappear" here because a coin or token never get disappeared from the market but only get delisted from the exchange due to no demand and regular fall in volume of the coin. The token is not active in the market that's why but it can still be traded if demand rise again.
If there is no demand how we can sure the token will have value? Most likely the value will gone slowly because the investor will think it's usesless when they still hold the token and it will be good if the token is sold now by them although they got loss. Unless the devoper still try to make the token still alive for instance they promoting back the token and update the new system that can attrack new investor until the old investor still believe the token will still has a value.