Argh, just realized from my bank statement that I got DCCed by The Astor, Luxury Collection Hotel by Starwood. Initially used my Amex as I always do but due to some complications explained by the front desk manager that it couldn't go through so had to use my Visa. When I signed the slip during checkout I ticked the RMB box and I forgot to check whether did they process it again before handing back my credit card...

Can't seem to find my receipt to do a dispute with my issuing bank. Oh well, lesson learned.