Who am I?

Think I may have figured out how my appraisal has become so poor in the eyes of my supervisor. Started work as usual. Went to the board where all the outstanding jobs were up on display and looked for my name. I was placed under the landing gear and hydraulic zones. So I looked at my jobs and thought I'd look if "J"s name was on the board. As "J" was off work for today's night shift because he attended fire training earlier during the day I wanted to see if they were so clueless as to expect him at work tonight. And sure enough they did. They placed him under the engine #3 zone. Finding it amusing as I did I thought I better let the zone supervisor know he would not be in. As I informed the supervisor. A rather interesting conversation unfolded, as such...

Me, " J won't be in tonight, so you;re gonna have to find someone else for engine #3"
Sup, " Huh what do u mean?"
Me, " He went for fire training during the day, so won't be in tonight"
Sup," But you're here!"
Me, " Huh? But I'm on landing gear and hydraulics"
Sup," No, thats for...umm... (has a look at the board)... P"
Me," Ummmm I'm P"
Sup," ... Your J aren't you?"
Me, " Errrr, no I'm P. Says so here on my pass, see picture of me... and below it my name"
Sup," You're not J?"
Me," Errr, nope... never have been"
Sup,"Oh...kay..." (nonchalantly removes "J"s name and carries on like nothing happened)

I mean I've only been working with this guy for over a year and held several conversations with him during that time. I mean if he thinks I am "J" then who else thinks that. I'm sure there will be more than one person with that idea in their head. After all the 2 of us hang out alot. Could also be why I am seen as a serious slacker. I mean after all I am slacking for 2, if you get my meaning.