Always delay the whistle a few seconds after the ORGINAL free kick has been noticed, to see if there is an advantage (advantage, not just possession) to be gained; if there is, arms up, and a nice loud PLAY ON ADVANTAGE!, if there isn't blow for the original free kick.
In this incident, unfortunately you were incorrect. You noticed the first foul, looked to see if anything was coming from it, nothing did, so it should have been given.