Strange acting hibiscus

I have a tri color hibiscus that I'd had for about a year and a half. I grow totally indoors, and this plant is in a west window, and I'm in the S. Calif. high desert so it gets several hours of afternoon sun daily. Its grown about 8" since I got it. It needs to be watered every other day, or it starts to wilt. Last night I noticed it was wilting, so I watered it before bed. This morning it was still wilted! I got really concerned, thinking I'd overwatered it instead of underwatered, and that its roots were rotting. The soil felt moist, so that had to be it, I thought. I immediately repotted it in cactus/perlite/peat mix that was barely damp. (By the way, the soil ball was moist and the roots were white, not brown like I would have expected with rot). Well, I checked on it a few hours later, and it was no longer wilted! What the heck? I've never had anything like this happen before. Its still looking fine, and its been 12 hours since I repotted it. Can anyone explain what happened?