Card Name: Bait Doll
Card Type: Normal Spell Card (Spell Speed 1)
Does This Card Target: Yes
Card Text: Target 1 Set card in the Spell & Trap Card Zone; reveal that target, force its activation if it is a Trap Card, then negate its effect if the activation timing is incorrect, and if you do, destroy it. (If it is not a Trap Card, return it face-down.) When this card resolves, shuffle it into the Deck instead of sending it to the Graveyard.
Ruling (Credits to Yu-gi-oh! Wikia)
*You cannot chain to a Trap Card that was forced to activate by the effect of "Bait Doll" since an existing Chain is in the middle of resolving.
*You cannot chain Stardust Dragon's Effect to this card's effect because it is not guaranteed to destroy a card.
*If the target of "Bait Doll" is no longer on the field (if it was sent to the Graveyard with "Emergency Provisions", or destroyed by "Mystical Space Typhoon", as a chain to the activation of "Bait Doll"), then "Bait Doll" is still shuffled back into the Deck. As long as the activation and effect of "Bait Doll" are not negated, the effect of "Bait Doll" that shuffles it back into the Deck still resolves.
*If Bait Doll was sent to the graveyard by Destiny HERO - Diamond Dude and then activated next turn, Bait Doll does not return to the Deck.
*As long as Bait Doll was activated successfully, it will return back to the deck at resolution.
How do you know if the Timing is Legitimate?
A trap that is activated by Bait Doll, must have an independent effect for its activation to be correct.
Ex. If Bait Doll targets a face-down card such as "Gift Card", the activation would be correct and the controller of Bait Doll would gain 3000, and return to the deck.
this is an example of an Illegitimate activation
Ex. Bait Doll targets a Set Solemn Judgement, Solemn Judgement will NOT activate due to Bait Doll and negate Bait Doll.
This is because Solemn Judgement does not have an independent activation.
Solemn Judgement CAN activate and destroy Bait Doll, before its full resolution.
Still don't know what an Independent Effect is?
An Independent Effect is an effect that does not require the activation or does not need to respond to the effect of another card.
Pretend Bait Doll isn't even there, if the card can be activated at any point of the duel without needing some kind of action from other side of the field, then it has an Independent Effect. If not, being forced by Bait Doll will make it's activation wrong and will be destroyed and sent to the Graveyard.
*NOTE: Independent Effect is just a term I use for my explanation, don't use it in a duel.