I'm looking at the spreadsheet card database from the Encyclopedia and I wonder if there is a way to determine whether or not a card can still be pulled from a pack? Is there a general rule of thumb for the availability of cards which came with events? In particular, I see some people place value on Tom, which I am assuming is the 3 star card from Soul Hunters. This card can still be found in the booster packs right now, and I have been using them as feeders before I saw a bunch of people with S>Tom in their profiles, which made me reconsider his value.
I guess I am trying to see if there is some way to determine whether or not a card is a reward (ie: limited copies out there), or if a card is added to the regular booster pack pool as a result of an event (ie: Tom). The reason I ask is I am interested in picking up some 3 star cards from the past witch event, (Piper, Phoebe, etc), but I am not sure whether or not these cards are still available. This puts me at a disadvantage in a trade.
I just want to develop a better foundation for the valuation of cards, so any help will be appreciated.