That sucks Juan! I think the yellow was on its way out. I have 3 tiny yellows with like 6 nems and they are still alive and kicking. Sorry for your loss...
I didn't know nems hosted yellow tangs..lol..j/k...but seriously sorry about your loss and even if you don't get it out, the nem will eventually spit it out as it's too big to digest. i had the same thing happen with a haddoni and a purple tang.