No, it's not. It is far from being dead.
I have Bittrex and BinanceUS. When I search for IOST on both the results of the search show... "no search found.. " or something similar. If I search for a coin like ADA on that same search it works as normal. My coin are on Bittrex and they show $0.00 and above that my BTC shows it current value. So damn frustrating!
It seems that it's not really on the market of Binance.us. But on Binance.com, it is listed with a lot of buy and sell orders. That really depends on the country where you trade and if it's not on Binance.us. Look elsewhere for another exchange that supports your country and has it listed.
It seems that this is the problem why OP couldn't find it.
I've been a part of the campaign before with IOST and I can definitely tell you, OP this is a legit project and it's still an active one on different exchanges but I'm surprised that it's not available in Bittrex. Maybe they have low demands of this coin on their exchange but don't worry there are exchange that you can easily to run as listed on this website.
https://coincodex.com/crypto/iostoken/exchanges/