Do not take "no noise" now as a good thing. Most of the time it's the bearings in either the idler pulley or the supercharger pulley itself.
THey will stop making noise sometimes before they fail but if you already had that whistling/squeaking noise you can be sure something is not right even if it went away temporarily.
Those two pulleys cause major damage when they grenade. I would not let it get that far. Also, if belt is worn it's time for a new one.
Take off the belt and spin ALL pulleys by hand one at a time. They are supposed to spin freely without rubbing, making any loud noises or wobbling.

You can also make a car "stethoscope" to listen to the pulleys (long screw driver or breaker bar etc). For instructions how to use that and what to listen to with the stethoscope watch the video here .But whatever you do, I wouldn't just disregard. Not sure how many miles on your car but especially the idler pulley fails quite commonly. They are not strong enough and made out of plastic while holding a majority of the strain. There is improved idler pulleys and also the pulley saver kit Needswings offers, which eliminates that issue.If it's your Supercharger pulley, you can replace the bearing which is easy and cheap. When that one grenades it's thousands of dollars potentially of damage.Are you using a an aftermarket supercharger pulley? ​​​​​​