I forgot my husband's niece had her appendix out in 2005. Is that normal?

I just turned 50 years old last month. I'm relatively active. I work, but mostly sit behind a desk or at a computer. I am an instructional designer, and I am also the academic coordinator for an English Language Center. I use my brain all day. I work 10 hours+ per day and most of my work is either creative or making decisions. I thought I had good brain function.

I'm good at remembering dates, when bills are due, schedules, events with friends, directions, and if I write down any information, I will never forget it.

Last week at Thanksgiving, all the "girls" were in the kitchen after dinner just chatting. My husband's niece (a regular at our house since she was little ), who is 24 years old now was talking about her appendix surgery. I was shocked. "You had your appendix out?! When?"

Her surgery was in 2005, she told me and I went to the hospital to see her.

I couldn't believe my ears. I have ABSOLUTELY NO RECOLLECTION of her having surgery and/or visiting her. My daughter told me who was there when I went. When my daughter named a certain person, I had a foggy memory of her face and I know that I would only have seen her in a situation like that. But I have no memory of our niece's surgery or me visiting her.

Is this a sign? Is it early onstage something? Is this just a normal age related memory loss? I was freaking out silently that whole night and all day today. I'm trying to remember, and I can't seem to recall or remember this event AT ALL.

Help me figure out what it means or where I can start researching. I am NOT going to the doctor unless I have some background information.