I Am Am Not A Regular Marajuana User, Maybe Once

I am am not a regular marajuana user, maybe once a week at most and in very small doses. Yesterday was one of those days that I did smoke, again a very small amount. Today, about 20 hrs after I smoked, I was given a random saliva swab drug test. I was able to administer the test myself, so I barely swabbed both cheeks for about 5 seconds each. I had also eaten 2 square meals drank maybe 3 pints of water, slept well and brushed my teeth. Should I be worried I will fail? Thanks in advance.