I was at first doubting you as I assumed surely the addresses were using same format.
Upon taking a look, I found the transactions in the history, obviously, and found them having error message for incorrect address. In the right corner of each transaction row there is a "Cancel" button.
Once you cancel these failed transactions manually, they do appear back in the balances, under delisted coins! Poloniex still has the coins. They have thus not deleted the wallets, like they never had as I still have dead coins there since few years.
Polo rules. Whether or not these days you think they should hire 100 customer service reps more and rent out an underground base and stuff it full of extra servers (which they should do with all their income these days... Fingers crossed.)