That is your best post yet NY. You would think that they would do that and see if you are giving identical urines but I have never heard of anyone noticing that. I have three friends who store frozen clean urine in 2 liter or gallon jugs. The dethaw them, shake up, and pour off a sample. Pretty much any sample that comes out of one big bottle would be nearly identical. No one has ever noticed or questioned. I wouldn't worry about the lab, if it is negative no one goes back over results. If your parents are testing you, I would only be concerned with them looking at the results.