。・・・。
An energetic voice comes right back at me. Guess I was worrying over nothing.
Literal
Energetic voice [subject-が] as-is is-returning-[come-てくる]. Needless-worry was-[past-だった] [question-かな]...
Narrative relief. そのまま ('as is, directly, without change') here describes the voice coming back just as energetic as expected — no diminished reply. ~てくる marks motion toward the speaker. 杞憂 ('needless worry, groundless anxiety') is a classical chengyu-style expression from a story about a man in the Qi state who worried the sky would fall — hence 'unfounded, groundless worry.' かな is the reflective question particle.