I've seen where a guy's air pre-filter was too heavily oiled and dripped in the vent hole of the fuel cap and get dq'd on fuel. It doesn't take much to cloud up the fuel enough to get dinged on a fuel test. As a tech man, this is one of those "I hate to" things, but a rule is a rule.
If stored improperly, (ie cap not tight, etc) alcohol can go bad. If the cap was tight and in a good airtight fuel jug, it should have been fine though. Also keeping the fuel jug up off of concrete floors helps.
BTW, new fuel jugs often have a release agent that, if not rinsed out thoroughly, will show up in a water test. Always rinse out new "alcohol" fuel jugs and fuel tanks with distilled water or straight methanol. Rinse gas jugs and fuel tanks with gasoline.
Figuring out if it's something in the tank, the jug, or introduced later, is the next step.
Check each with a glass container and distilled water. Also -- you need to use "distilled" water, not purified water or drinking water - they are different.