I think it might be Once Upon a Star. OUaS was a limited edition 15ml release about 6 or 7 years ago and did have a gold cap, but I'm not sure about the chain.
You can try sending mail to [email protected]. Or reach them at:
Thierry Mugler Parfums
10 Cavendish Place
W1G 9DN London
020 7307 6700
020 7307 6705
Wish I could tell you for sure, but I hope this helps.