Mismemory or Insanity?

My memory is hopelessly flawed, but my realization of its unreliability reached new heights today.

Here's the story:

Last week John from work told me a story about how his daughters had 2 hamsters. They believed them to be 2 boys, but with hamsters, you never really know. After an expectedly long life for a hamster, one of the hamsters died. A week or so later, John and his family went on vacation (I assumed asking someone to feed the remaining rodent while they were gone.) When they returned, they noticed a baby hamster cuddled up to the older hamster. They assumed that perhaps she was a female until they realized, that the baby hamster was in fact a mouse that had crawled into the cage and befriended the hamster. A few weeks later the remaining hamster died, and Johns daughters cared for the mouse for a couple years until it too passed.

That day I instant messaged Chad to remind me to tell him about how John's daughters acquired their pet mouse. I didn't remember to tell him until this morning.

Then at work, I informed John that I had told Chad about the mouse and the hamster. John, looking at me like I was crazy, but still with interest at the story, listened to me retell the story I could have sworn he told me last week.

He said that his family has never had 2 hamsters at one time, and his daughters would not adopt a mouse because they don't like rodents with long tails. He acknowledged that it's possible he told me that story about a friend, and he just doesn't remember the story or telling it, so he's going to ask his family if it sounds familiar to them. I find it unlikely that he would have told me the story and then not have even recognized it when I retold it.

I also asked around the office to see if anyone else had told me the story, and they claimed they hadn't. I even remember details like where I was standing when John was telling me the story, so my best hope is that he told it to me about someone else.

Chad confirms that I did send him the IM that day, which means I made the mistake pretty soon after I perceived it to have happened.

So here is the question:

Did John, or someone, actually tell me the story, and I mixed up the details of the family in the story and the where and whom told me?

Did I dream the story and the telling and somehow transfer that to reality?

Did I make up the whole scenario in my mind and then mix that up with reality?

Did I hallucinate the situation?

Is this a reality check about the condition of my mind, or is it just a result of a temporarily stressed and busy life?

Well... maybe time will tell... for now, back to work. Now what was I doing?