First, to answer your question: no, I'm pretty sure it doesn't matter. Unless they do DNA comparisons...which I doubt McDonald's does much of these days.
Here's a suggestion: How bout you get off the drugs instead? Some of us busted our asses to go through college and stay clean all the time, just so people can pull **** like this and hang on to all the damned jobs. It's too bad the companies are such pussies that they don't want to institute any HARDCORE drug testing...but hey, I guess if I was some greedy company I wouldn't want to chance losing 70% of my staff either.
You're lucky. In the AF, my friend said they hooked him up to some kind of ****ed up machine that cut his arm, and that from that they did some kind of insane test where they were able to tell him if he ever did any drugs in his entire adult life.