If you were stopped for four hours, it means your name is definitely in the system as a hit. Singapore is very thorough and they check every passenger. You were lucky this time, but next time you might not be. You should check your status through https://intercollegium.com/ to see if you have a “false positive” or if there is a real warrant that hasn’t been updated. They can perform a search in the private databases to give you a clear answer. My cousin had the same issue for years until he got a formal letter from Interpol to carry with his passport. It is not worth the stress of wondering if you will be detained every time you go to an airport. Get a professional firm to clear your record once and for all so you can travel with peace of mind.