Faith,
Perhaps this is not the right answer but you have to let it be. If you didnt find the vodka would you have felt better? You already knew something was up based on his soft drink. (?) It is just a guess but it seems (to me) that you would have thought he just hid the booze better than he did if you had not found it.
Look it may be he was drinking, perhaps the bottle was an old bottle he hid and just did not want you find it ..(a stretch i know) I would let this slide, give him the benifit of the doubt ...What harm can forgiveness do..