Thank you for your answer.
No. 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. You can test it, of course, by giving an injection before bedtime and checking your glucose upon awakening and compare it with what usually happens.