I think the chart at tamagotchi.com would be the more accurate one to go by. They haven't got all the characters but the one you are talking about (same as I have) is a Hinatchi. I got that one way different than you. I never left mine alone. I got one because my daughter got one and let me play...
I have a toddler (mizutamatchi) and I think he hates hamburgers cause all his hearts went away, he turned his back and he was in a bad mood. Has that happened to anyone else's mizutamatchi? Or did something else cause this?