Scientific question answering is useful only when readers can recover the papers and evidence behind an answer. Yet many benchmarks either provide the source document or score only the final response, obscuring failures in literature retrieval and evidence localization. We present LitTraceQA, a literature-grounded question answering benchmark in which a system must return a connected trace: canonical paper identifiers, typed evidence locations, and a checkable answer. The collection contains 4,978 unique questions grounded in 4,859 papers and covers tables, figures, text spans, equations or algorithms, and citation contexts. Of these questions, 64.85% require multiple papers; answers use multiple-choice or structured-table formats; and 61.9% are missed by every memory-only challenger used during construction. We describe a generate-and-ground-challenge pipeline and an evaluation protocol that reports paper retrieval, evidence grounding, answer correctness, and strict joint success separately. LitTraceQA therefore tests whether scientific QA systems can produce answers whose provenance is inspectable, rather than merely plausible.