Having several kids, I have done this at least once every year from someone either testing what can make it or dropping something in as the water is going down. Often no one says anything until it needs attention if you know what I mean.
The first time that I ran into this problem I thought to call a plumber who quoted me $100 which changed my mind to try doing it myself. The only cost is time and most likely the cost of a wax ring. (The style I use in this video is reusable and the only style that I use anymore) KZfaq wasn't really established then but would've been nice to boost my confidence in what I needed to do. I recorded this and hopefully someone finds it helpful.
The wax ring should always be replaced unless it is a reusable style like the one in the video. It is also much cleaner for the next time the toilet needs to come off for another traffic jam or even a full replacement.