Document did not contain stellar_address

Question

I'm a Stellar beginner trying to validate an account I just created as follows:

val server = FederationServer("https://horizon-testnet.stellar.org")

val keyPair = KeyPair.random

for {
  resp1     <- TestNetwork.fund(keyPair) if resp1.isSuccess
  acct      <- TestNetwork.account(keyPair)
  validated <- server.byAccount(PublicKey(keyPair.pk))
} yield {
  println("Validated: " + validated)
}

the error I get is:

[error] Caused by: stellar.sdk.inet.RestException: Document did not contain stellar_address [error] at stellar.sdk.FederationServer.validate(FederationServer.scala:58)

due to this validation

Please explain why this is so? Was I meant to provide the stellar_address at creation?

(tag should really be scala-sdk but I don't have enough reputation to create it :-( )