Gem Store outfit missing
Whoever was wearing it last is still wearing it, even though you can’t see it, remove it, or swap into it. You need to take that character to the Black Lion Trader (Armorsmith) who is located by the regular Black Lion Trader in any of the large cities and he’ll exchange your old town clothes pieces for the new versions. If you don’t remember which character was wearing it, take them all to talk to him; he’ll give the others tonics for their old town clothes.
If you were wearing multiple pieces of an outfit, like the Mad King outfit, he’ll give you multiple items. The reasoning there is that if you deleted, say, the gloves, but kept that boots, you’ll get a full unlock anyway. Once you use the outfit item that the Black Lion guy gives you, it unlocks the costume for all characters on your account, so you don’t need to keep the extra items, as you can’t sell them or have any real use for them.
Tonics, on the other hand, you seem to be able to sell, so it’s up to you what you do with them.
I hope that helps! Regardless of what you think of the change in the town clothes system (“Boo!” in my case,) I think we can all agree this step wasn’t clearly explained for a lot of people.
Go see Black Lion Armorsmith in any City’s TP area.
Edit: Ninja’d
RIP City of Heroes