It is possible that your tamagotchi was getting ready to use the bathroom before you pressed the "c" button.
How to find the bathroom!:
1. Wait till your tamagotchi is kind rocking/moving back and forth a little tiny bit (this action is another animation), and is in one position, as opposed to the normal jumping and walking around. It also has a strange expression on its face, kind of like constipation. lol
2. QUICKLY (I cannot stress "QUICKLY" enough), press the toilet icon (push "a" 3 times, then "b" once) to "flush the toilet.
3. When the tamagotchi is acting as is described in #1, the tamagotchi is getting ready to go to the bathroom. By flushing the toilet while your tamagotchi is doing this, the tamagotchi goes to the bathroom in a toilet! Ta-Da!