Three hours is the fastest I've seen a acoustic come back to normality. It must have just been so dry and combined with the added moisture, plastic over the hole and hot temp to make it sweat the guitar just absorbed it faster than usual. The last time I had a problem was on another acoustic that had a cracked top with a wide gap and a couple of braces had let go. That needed a bowl of water sat inside it for a week to come back together before I could glue the bracing back on and install some cleats over the split in the top. These cheap humidifiers I have I just run under the tap and then shake them off. They all seem to work the same, I like these because there is no dripping etc but whatever holds water and doesn't wet the guitar works as good. I had another play on it a few hours ago and it sounds much better now, it was sounding kind of cheap and boxy like a low end starters acoustic. It now sounds fuller and richer like its old self. I've been leaving the dampened humidifier in it when not playing it and will let it take in some more moisture over the next day or two.