I thought this relivent

To clarify it was up and, then disappeared, and then came back again

Do you mean what is going on in that episode? They track down a guy who is using animal parts to absorb special animal powers. Dean finds the heart, and offers it to Sam as a joke. *Spoiler* (Dean drinks a special potion to "connect" with a dog to find out what the dog saw at a crime, and ends up acting like a dog himself).

That's the episode after this one. The one above is the one with the Horseman Famine, and there are people starving for something. But that heart has the mark of Cupid on it, which means he paired that heart and someone else's.

Oops!

Yup