Why can't I play a card for its alternative cost after searching for it with Bring to Light?
It is because Bring to Light and Evoke are both alternate costs, and you can only choose one alternate cost when casting a spell. Since Bring to Light is what is giving you permission to cast the Revilark in the first place you have to use its alternative cost, you can't Evoke it (by paying mana) off of Bring to Light. Compare this to Omniscience which also gives your Revilark an alternate cost, in this case you could choose to cast it without paying its mana cost or pay its Evoke cost but not not both (paying no mana for its Evoke cost).


  117.9. Some spells have alternative costs. An alternative cost is a cost listed in a spell’s text, or applied to it from another effect, that its controller may pay rather than paying the spell’s mana cost. Alternative costs are usually phrased, “You may [action] rather than pay [this object’s] mana cost,” or “You may cast [this object] without paying its mana cost.” Note that some alternative costs are listed in keywords; see rule 702.
  
  117.9a Only one alternative cost can be applied to any one spell as it’s being cast. The controller of the spell announces his or her intentions to pay that cost as described in rule 601.2b.
  
  702.73a Evoke represents two abilities: a static ability that functions in any zone from which the card with evoke can be cast and a triggered ability that functions on the battlefield. “Evoke [cost]” means “You may cast this card by paying [cost] rather than paying its mana cost” and “When this permanent enters the battlefield, if its evoke cost was paid, its controller sacrifices it.” Paying a card’s evoke cost follows the rules for paying alternative costs in rules 601.2b and 601.2f–h.