I Had Back Surgery August 14th And In October I

I had back surgery August 14th and in October I was given another script of Vicodin 1/325. Bottle said 3 time a day or as needed so when my therapy is bad I may take one at night ONLY and not every night but just to keep it simple I would rather know this answer. Will it even show up if I was picked for a random DOT drug test the next afternoon? I do not abuse drug. I had a l5-S1 fusion with instrumentation. Thru the front and back, they cut. However just would not rather cross that bridge. Ive heard that they do not check for synthetic opiates which is Vicodin. Is this true?