costumes deleted before 15th april, 2014.
For costumes you’ll have to contact support. I was able to get my celebration hat back this way as they could see in the records that I had purchased one from the gemstore at that time, but when the wardrobe came along it was no where to be found for me.
For dyes however you’ll just have to deal with the lost dyes because there is likely no way to tell what dyes you had.
Submit a ticket and give them the info on your missing hat and hopefully they’ll give you a replacement like they did for me.