Notation to differentiate between guitar notes timbre?

Sheet music is more of a guideline for us guitarists. All it shows is the note that MUST be played, but as everybody's favorite little black dots are not instrument specific, there is nothing that says what fret it should be played on for a guitar. That is why tabs exist in a nutshell, so you're gonna have to rely on your contingency plan if you absolutely want it played on that string. Sheet music means you can form the chord any way you want, while tabs say "put finger here".