Bisol320,
Tomycase, is correct, we need something more. 2D or 3D? Screenshot or gif or what's happening.
For example: if it's a 3D game one object could overlap another object and that would cause it to vanish.
Or if it's 2D (or 3D) you could have the name spelled incorrectly in the code (I've done that more times than I like to admit)
It could be a dozen other things, but without more information we're just making the obvious guesses.