Linguistic question

(I ask this here because it seems that those who use IPA and X-Sampa linger longer in this forum.)

Are linguists (those who studied linguistics) able to identify ALL sounds in a given language? For example, would someone who graduated with a bachelor's degree be able to designate every sound in Language X with a symbol recognizable to other linguists?

I can imitate the sounds fairly easy but, I recently came across a vowel sound I couldn't find a way to notate.

I would say no, because for starters one would probably have to take into account all dialects and idiolects in question, which is pretty daunting to begin with, and because systems like IPA and X-SAMPA are rather coarse-grained in what they represent in reality and do not actually cover all possible sounds that might be used in a given language (even with diacritics). Furthermore, they would have to take into account variation in the actual realization of a given phoneme, which may be quite significant even on an individual basis.

Thank-you, Travis.