^^^ LOL, that's ok.
Yeah, if the vet will accept a poopy that you bring, will be much easier than the tech trying to stick the thing up his sore bottom. Not fun.
Please let us know what happens tomorrow.
It could be possible that he ate something bad that you didn't see, not just the food change. These guys are so small that just a bit will make them sick. That is why it's so important to get to the vet and find out, and not just wait and see.