Scala Issue?

issue.scala

import org.json4s._
import org.json4s.native.JsonMethods._

sealed trait Entry {
  def value(): Any
  def key(): String
  def public(implicit dicts: Map[String, Dictionary[Entry]]): Boolean = true
}

case class ContextUriEntry(uri: String, context: String) extends Entry {
  override def key(): String = uri
  override def value(): String = context

  override def public(implicit dicts: Map[String, Dictionary[Entry]]): Boolean = {
    context.trim.nonEmpty
  }
}

abstract class Dictionary[+T <: Entry: Manifest]() extends Map[String, T]  {
  implicit val formats = DefaultFormats

  val data: Map[String, T] = parse("""[{"uri": "http://rdf/tag/Tag", "context": "Context Content"} ]""")
    .extract[List[T]]
    .map(e => (e.key().toLowerCase, e))
    .toMap[String, T]

  // Map implementation
  def get(key: String): Option[T] = data.get(key)
  def iterator: Iterator[(String, T)] = data.iterator
  def +[V1 >: T](kv: (String, V1)): Map[String, V1] = data + kv
  def -(key: String): Map[String, T] = data - key
}

object Dictionary {
  case class ContextUriDictionary() extends Dictionary[ContextUriEntry]
  def getByName(name: String) = name match { case "ctx" => ContextUriDictionary() }
}

object Loader {
  val dicts: Map[String, Dictionary[Entry]] = Map("ctx" -> Dictionary.getByName("ctx"))
}

repl.txt

scala> :paste /tmp/issue.scala
Pasting file /tmp/issue.scala...
import org.json4s._
import org.json4s.native.JsonMethods._
defined trait Entry
defined class ContextUriEntry
defined class Dictionary
defined object Dictionary
defined object Loader

scala> implicit val dicts = Loader.dicts
dicts: Map[String,Dictionary[Entry]] = Map(ctx -> Map(http://rdf/tag/tag -> ContextUriEntry(http://rdf/tag/Tag,Context Content)))

scala> dicts("ctx").data.filter { case(u,v) => v.public  }
java.util.NoSuchElementException: key not found: Context Content
  at scala.collection.immutable.Map$Map1.apply(Map.scala:108)
  at ContextUriEntry.public(/tmp/issue.scala:51)
  at .$anonfun$res8$1(<console>:38)
  at .$anonfun$res8$1$adapted(<console>:38)
  at scala.collection.TraversableLike.$anonfun$filterImpl$1(TraversableLike.scala:248)
  at scala.collection.immutable.Map$Map1.foreach(Map.scala:120)
  at scala.collection.TraversableLike.filterImpl(TraversableLike.scala:247)
  at scala.collection.TraversableLike.filterImpl$(TraversableLike.scala:245)
  at scala.collection.AbstractTraversable.filterImpl(Traversable.scala:104)
  at scala.collection.TraversableLike.filter(TraversableLike.scala:259)
  at scala.collection.TraversableLike.filter$(TraversableLike.scala:259)
  at scala.collection.AbstractTraversable.filter(Traversable.scala:104)
  ... 39 elided