[confirmed]Cobra Trap: no alt cost

[Korath]

Describe the Bug:
Cobra Trap can only ever be cast for its full cost, never its alternative cost of .

Which card behaved improperly?
Cobra Trap.

Which update are you using? (date, name)Which type? (duel, gauntlet, sealed deck)
dev master head, 859619b. I see no evidence of it ever being castable for its alt cost in previous versions going back to 3.0 in January 2012, either, though.

What exactly should be the correct behavior/interaction?
You can cast it for just if your opponent's spell or ability destroyed (or buried) your noncreature permanent this turn. Note the exceptions listed in the card's rulings: sacrifices, exiling, removing all loyalty counters from a planeswalker, triggering an ability you control that does the destruction.

Because Manalink still has the old fourth-edition damage prevention and regeneration steps, it's possible to get a creature that's scheduled for destruction due to damage or deathtouch to stop being a creature before its destruction is finalized (by sacrificing an Animate Artifact or similar enchantment to pay a mana cost, for example). This shouldn't be enough to allow casting Cobra Trap for its alt cost, either: it's not the spells and abilities that deal damage or grant deathtouch that cause the permanent to be destroyed here, it's a state-based action, rule 704.5g and 704.5h.

Are any other cards possibly affected by this bug?
Nothing else is even superficially similar, as far as I'm aware.