Indestructible creature gets destroyed.

[Amarquez]

My 3/3 Darksteel Juggernaut got destroyed by a 3/3 Scuzzback Scraper with First Strike and Wither. Darksteel Juggernaut is supposed to be indestructible and go to minus numbers instead of dying.

[MarSprite]

Wither reduces the toughness via -1/-1 counters, eventually causing it to have a toughness of 0 or less. Creatures with a toughness of 0 or less are sacrificed.
Note if something sustains damage equal to its toughness, it is destroyed.
The word of the hour is sacrifice, indestructible does nothing against sacrifice, exile, control, and return to hand, among other things.
This is not a bug in Wagic, this is the way MTG works.

Pardon, I researched to reassure myself that I was correct, and so far as terminology goes, it seems I am mistaken, it is not sacrificed, it is "put into the graveyard" as a state based effect that happens when a creature has 0 toughness, something else indestructible is vulnerable to..

Still, not a bug.

[Zethfox]

302.7. Damage dealt to a creature by a source with neither wither nor infect is marked on that creature
(see rule 119.3). If the total damage marked on that creature is greater than or equal to its toughness,
that creature has been dealt lethal damage and is destroyed as a state-based action (see rule 704). All
damage marked on a creature is removed when it regenerates (see rule 701.11, “Regenerate”) and
during the cleanup step (see rule 514.2).

700.4. If a permanent is indestructible, rules and effects can’t destroy it. (See rule 701.6, “Destroy.”)
Such permanents are not destroyed by lethal damage, and they ignore the lethal-damage state-based
action (see rule 704.5g). Rules or effects may cause an indestructible permanent to be sacrificed, put
into a graveyard, or exiled.

704.5f If a creature has toughness 0 or less, it’s put into its owner’s graveyard. Regeneration can’t
replace this event.

it is not destroyed by the wither, instead gets put into the graveyard as a state based effect.

[Amarquez]

Oh, I see, it's quite confusing at first. Thanks for the clarification, I should have researched more at first.