Lost in Thought

Oracle Text

Enchant creature

Enchanted creature can't attack or block, and its activated abilities can't be activated. Its controller may exile three cards from their graveyard for that player to ignore this effect until end of turn.

Card Rulings

10/4/2004 You can take the “exile three cards” action any time you have priority without using the stack.
6/8/2016 Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keywords are activated abilities and will have colons in their reminder text.