So, I noticed a weird thing going on with achievements that require items in your wardrobe and I'm not sure if there's a quick way to fix it but I thought I'd bring it up?
If you quickstock your items into your wardrobe, they show up in the achievement list immediately. If you click add to wardrobe on the shop search page after purchasing, they don't. I'm not sure how long it would take to actually show up since I'm very impatient, but I removed and re-added the same item manually and got the achievement immediately.
It only takes a few minutes to show up usually, but even quickstocking sometimes does not make items show up quickly. I almost always encounter the quickstocking problem during site events (lots of people online) or after I have lent someone several rounds of items. It seems to just be a thing with the site/wardrobe cache. But removing/readding items to the wardrobe like you said usually resolves it. If not, well, I'm a fairly patient lender.