Code P0446 and a question

A while back I had been getting the P0442 after screwing up with the fuel pump O-ring. I addressed that three months ago and the 96 4dr S-10 saw maybe 500 miles. No CEL until yesterday, of course it's happening now that I have to get it and two other vehicles inspected this month. My buddy cleared the code and today I drove 21 miles with no CEL, he told me I needed to drive at least 50 miles before the states test equipment will pass it. So my questions are why didn't it turn back on? and does the sampling work like code P0442 that only tests when the tank is between 15% and 85%? TIA

evaporative emission control system ''valve malfuntion'' if pcm sees a fault in system more than 1 time consecutive it will set code it may have seen a fault but was just intermitten.if it does'nt see this again then you can clear code & be fine.it also could be something starting to fail but you'll need to wait to see if it triggers ses again.hope this helps/makes sense Good luck