Your issue was that you clicked through from TripAdvisor to Agoda, and that was the only way to get the price. Starting a fresh browser didn't help since a cookie was left. You should have tried going with a different browser, preferably in incognito. I've witnessed this across all the board, but Agoda is notorious for having different rates for clicking through vs direct search. Heck, I've had Agoda tell me they didn't even offer a hotel without clicking through...