The F/O (typically) does a walk around pre-flight... I'd be shocked if s/he wouldn't have picked up on it. But to answer you question, I'd say you were right. Why not? I was on a recent DL A320 that apparently had a more than unusual sound during taxi (besides the hydraulic x-feed pump groaning) that did turn out to be an issue, that pax in the exit row pushed the call button for. If it's nothing, it costs nothing.