Missing party outfit

May I ask please, what exactly do you mean by party outfit? There isn't any category of outfits by that name in TS3 CAS. There's Formal Wear and then there's things like masquerade costumes sims may spin into for a costume party if you have Seasons, but perhaps you meant something else like a particular outfit that you were expecting to show up in one of the existing categories?

Ah...no. Different kinds of parties dictate different kinds of outfit types. It would be Formal Wear for dressing up types of occasions, Swimwear for pool/beach parties perhaps, and you can design any kind of outfits you like out of Everyday outfits for various other kinds of get togethers. For costume parties, the Special Outfit category is called upon in-game, but you wouldn't see that in CAS. Unless of course your sim has the Inappropriate or Insane traits, in which case we might expect to see them wearing a snorkel mask, underwear, and bunny slippers to a formal event just like those of us with these traits do in real life. :)

I think TS4 might have a category especially for parties, but a player of that game would have to confirm it,

It's been awhile since I've played TS3, I thought there were seperate outfits for things like weddings and then there were outfits for parties. I could be mistaken as I haven't played in forever, is there only a formal outfit to wear to parties?

Ohhh okay! Yeah I play Sims 4 and we have formal and party outfits. It basically depends on what you make party-goers wear to the specific party, such as a wedding, you would do formal. If you went to a restaurant they would have a dress code as well. I must've got everything mixed up as TS4 CAS has a party category ? thank you so much for your help! I thought my game got broken for a second ??