ArtlessMonster, at some point in my life I thought I have Alzheimer's. I didn't know the name, but I knew the disease that affects memory. I was 12 at the time.
Many people don't realize that we live in the world hugely packed with information, attention attractors, actions, decisions, memories and so on. ]
And humans are not naturally suited to managing all this. We can learn if taught properly, but if not, we can have the kind of problem that you are having.
Don't worry. Forgetting that you have something on the stove, especially if your attention is diverted somewhere else is normal. It makes you a bad cook - good cooks always watch their dishes, but it doesn't make you extremely aloof. If this wasn't a common problem, kitchen timers would not be invented.
I suggest you try GTD task management system. Do a search on Google if you don't know what it is. In a nutshell, it is the system of tracking tasks where you don't rely on memory at all to recall your tasks. You just write everything down. When I did it for the first time I've realised that I had several hundreds of things that needed to be done. I even remembered them somehow, but there was no chance I could recall them at a proper time. For that alone GTD deserves the hype it has. With tasks out of the way, you may want to evaluate how bad or good your memory really is. As far as I understand you've successfully recalled the situation with your friend over IM and the cookies in the stove. I would expect much less from a person with "absolutely awful" episodic memory. And this episode came across as very emotional.
But if you are worried, try writing a diary, or private blog every day. In the evening set aside the time to remember the events of the day. I think you will be amazed how much and with what details you will recall it. Plus you will have an avalanche of associated memories from the past. Write them all down as well. For a few first days you may have a busy time doing it, but your mind will get the idea, that whatever it has remembered is actually important for you. And it will improve your recall skills.