moody'sif it dropped due to the Moody's downgrade then absolutely it's a buying opportunity. Bond ratings companies are notoriously way behind the curve - the bonds should have been down-graded a year ago when prices were on their way down. Kind of a joke that they re-rate the bonds when oil is now poised for a rebound. So all they are doing is catching up with what the market already knows.
FYI - Lehman Brothers bonds were rated by Moody's as A2 up until they filed for bankruptcy and they were slashed the day they filed. Talk about calling the horse after the race!!!