Lantus can be left unfridgerated for weeks at room temperature and not be spoiled, as long at temperatures are reasonably cool, and the liquid remain clear. This is
not, of course recommended. And
not desirable. On the other hand, it will lose effectiveness, which means you may not be able to precisely titrate a dose. It's kind of expensive, so there is no need to discard it for such a short period without refrigeration.