Interesting. Thanks for the details -- I figured it would be a little shady if it was a 'flash' announcement of the de-listing. It's easy to miss emails / tweets / notifications sometimes. Lord knows my fiat bank still has my address from about 10yrs and 4-houses ago -- probably sending various notices there still.
I don't use Poloniex myself, and don't store anything on exchanges unless I'm actively trading / converting things.