If your question is did you lose the 5lbs because of dehydration, I suspect the answer is yes and that you'll notice that it returns when you re-hydrate (after your hangover ).

Hope you read no judgment into the response b/c I do purge my booze so that I don't get sick and I weigh myself daily too even tho I know I shouldn't. Ah well. We're all works in progress.

All the best
Bubba