Movie had a hole in it that made it fall apart for me (SPOILER!)

Rating: 6/10 (12 June 2011)

At the end of the movie Shelby explains everything about what really happened to the person Leonard was looking for. my question is where is that "I've done it" tattoo through out the movie. A scene shows Leonard's wife rubbing his "I've done it" tattoo but where is it when Natalie and Leonard look at the mirror when they are reading Leonard's backwards tattoo. Its a good movie but it fell apart for me when i figured out the hole. Because if Leonard would of saw his "I've done it" tattoo at the start of the movie, he would need no reason to find that burglar because he would seen on his chest that he has killed him! Still a good movie though.
I'm just guessing here but maybe this is why the academy awards didn't nominate memento for best picture because they probably figured out the hole too.