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An episode with its own fake commercial? That's usually a good sign...

And it is!
Final Score:
The S4 episode in question was "It's the Great Pumpkin, Sam Winchester" #4.07 and the released villain who counted as a seal break was Samhain. I knew I would butcher his name's pronunciation, hence my not even bothering to try.
Also I double checked the timeline. The pilot episode starts on Oct 30th and runs through Nov 2nd. Dean arrived on the 31st and the ghost hunt seems to have taken around a day and a half to two days. So yes, the last time Sam saw Jess alive would have been Oct 31st - which you think would be a larger impact on his life than throwing up on a school crush. Solid episode otherwise.