Hi,
First of all, I sympathise with you. This should not happen to a 11k watch.
Two issues here:
a) Dial defects can happen. A good friend of mine owns a 80,000 dollar watch - a screw on the dial of the watch started to rust after a few months of purchase. My friend went back to the boutique, watch goes back to Switzerland for 6 months for repairs as it is covered under warranty. That's how watches are fixed if there are issues. No one would offer you a refund. $11,000 is not a small sum of money under most circumstances and can be many months of apartment rent for many people in Singapore, but in the watch collecting world, 11,000 is an entry model watch, so do not expect to be treated in a VIP fashion in the shop. That's the reality. Not saying who is right or wrong here.
b) If the Manager had treated you rudely, you can write to the management to register your unhappiness with the service, provided you behaved in a civil manner yourself at the boutique. If both of you were shouting at each other, very hard to say who is right or wrong.
My 2 cents.
By the way, buying at boutique is not always better. You have nice young ladies to serve but in reality buying at a boutique/showroom is often more expensive than at the retailers.