Probability or Imperative
A couple of clarifications could help here. When you say there "should" or "ought" to be a word for something, do you mean "there most probably is, or is to be expected" (there should be a cliff on the other side of the road) or "it is an imperative to be so?" (there should be a sign on the wall indicating the rules)
In the first case, I would ask if the feeling indicates you have confidence that there is a word for some thing or concept but you don't know it. This might be generally described as having an inkling, a hunch, a notion, suspicion, or intimation.
In the second case, you would be asking (or stating/suggesting) that there be a word for something that doesn't yet have a word representing/defining/describing it, like making a case for an English equivalent of the German schadenfreude, for example.
Intuition vs. Knowing
You indicate this is a feeling which implies an unconscious, spontaneous knowing that could not be reached through normal deductive, inductive, or non-monotonic reasoning heuristics; it's an intuitive knowing and not one gained from accumulation of knowledge. It is unconscious in that one does not consciously decide to have this feeling and spontaneous in that while it may come as an epiphany, it does not come when called (think about one's creative muse).
This would contrast with, say, reaching that conclusion (that there ought to be a word for...) from a logical, possibly emperical, bit of reasoning with what you know about words and lexicons and etymology and so on. Then I'd argue it would be less of a feeling and more of a proposition or supposition (that there ought to be a word for...) or even a conjecture or thesis.
Not to be pedantic here, but one can feel that there ought to be...or think/suppose that there ought to be...and that modality of knowing (feeling vs. thinking) can decide which word to use.