Friends say tail light out, but it isn't ????

My wife's co-workers have told her 3 times now that her passenger side running light is out. Every time I check it it is fine. I keep telling her I can't fix it if it isn't broke! So I read a thread about going to LED style, but I'm not sure this is the solution. If the bulb was out isn't there some dash warning that would also alert of the problem? I removed/replaced the bulb (not with new, just original) hoping it was a connection issue. I shook the wired around causing vibration hoping that would duplicate the problem-again nothing. So either her coworkers are just messing with me or this is a real problem! ( I really doubt they are messing with me) Anyone have a clue?

 

Should I replace with the LCD type, and if so, do both?

 

Thanks a lot. Off to the parts store...

 

Update: when wife came home today it was actually really out! Funny thing that this started over a month ago. Not going to try to understand it, but it is odd. I have seen some odd things with electrical stuff before. What doesnt really make sense is that it wasnt working when she started the car after sitting all day and then it was working by the time she came home (an hour drive). Usually electrical oddities act funky after heating up. Anyhow, like I said, I'm not going to try to figure it out! By the way i went with regular 2825 bulbs about $6 for two.