That sucks dude..If you have to retake it, will they require you to get another medical?
When I got hired ten years ago they lost my drug test and didn't say anything for two months. I ended up having to take a second drug test.
Hopefully they can find it and it wont be that big of a problem. I dont mind a slight delay because I have a friends destination wedding in the middle of April that I dont want to miss. But I'll be bummed if this takes a while to resolve. If I just have to go retake a drug test that's no big deal though.