Does pdfTex produce warnings when it doesn't find the word hyphenation pattern?

In my document I use babel package and load several languages for correct hyphenation.

usepackage[icelandic, latin, czech]{babel}

I add manually words that babel package doesn’t know.

begin{hyphenrules}{icelandic}
hyphenation{
  pla-tó-nskt
}
end{hyphenrules}

I wonder if I can find in log file warnings when the pdfTex using babel package tries to hyphenate word that it actually does not know. That would help me in adding the words into hyphenate rules.