I Smoke Marijuana Once In The Past Two Weeks, Just

I smoke marijuana once in the past two weeks, just a couple hits of a joint. Before that I had not smoked for seven months, since the middle of October. Now I find out I may have a hair test for a solid job within the next two weeks. Most evidence I see on the Internet states that I've nothing to be worried about since low and infrequent use is not detectable in a HFT or Urinalysis. Just wanted to see if a clinician could provide some insight on the matter. Is there validity to what I've heard?