Turns out, Slime had sold the set to both of you. There's no record of that specific set on discord #market or the forum Market boards. Zwar was unfortunately unable to provide evidence of purchase but said he's renouncing ownership of the set. This doesn't help because Slime may have sold the set to more people.

Skeez, the initial statement stands. You're unfortunately unable to sell the set (but you are allowed to wear it) if you could private message me the screenshots of DMs or whatever evidence you're able to provide.

I'll try contacting Slime.