Quest Lost & Found
 

during the quest, Party Planning I accidentally deleted the outfit I was supposed to wear at the docks. Is there a way to get another outfit ?

the outfit can be found in the haystack behind Del Seleth - located in a small building behind Windhelm Bank (if you lose/destroy it, you can get another from here)

Hope this helps

And normally you could delete the quest and start it over again (if your quest progress allows it to be deleted without having to do several pre-quests again :( )