Sorry it's rather late... but here are my other two stories.
Two dogs came in having eaten some blood pressure medication of the owners. Again the task was to make them vomit. This wasn't too difficult. I put them back inside after they had, and put on gloves to poke through what they had eaten. One (a little labrador, and the suspected culprit) had appeared to have vomited newspaper, the other (an older cocker) vomited some bizarre plastic shreds and something orange. The doctor went and spoke to the owners and explained what we had found, and they insisted that the pills were purple. So we kept the dogs for monitoring, and fed them activated charcoal just in case. Before we left for the day I gave them a bowl of water. The little lab drank the whole bowl, and then vomited all of the charcoal I had fed her. Darn.
The next day we have a client come in with a dog who was vomiting daily, pretty much in the mornings. The dog had recently come in for a urinary tract infection (I think) and was on antibiotics for it. She had also recently been boarded, and the throwing up started after the boarding. Some antibiotics can cause upset stomachs, so we asked the client about the medication. She happened to have it with her, and took a bottle of medication out of her purse. My doctor took a look at the medication and took a few minuites, but eventually broke it to our client (as nicely as she could) that this medication was not the dog's, but hers. It was some variation on Meloxicam. The client realized that it was this medication that she had given her dog that morning, and was unsure of if it had been given other times also. She was pretty upset by this whole thing of course. We offered to do bloodwork, and put her dog on fluids to get everything out of her system. The client went home and called us to let us know that the dog had only received one of the pills of antibiotics, and had gotten her medication the entire time the dog was boarding.