even with code I write myself, I can't remember the line by line implementation on the entire code base. To be honest I often forget implementation details on code I wrote last week.
Also, almost every time I go back to review code I wrote more than a year ago, my first reaction is "jesus, that's a stupid pattern/implementation. Why did I do it that way?". I've been a professional developer for about 12 years now and I suspect that will never change.