I've never done it, but some people say condoms work well...and if you're young and single they're probably always handy as well.
Sorry about your first experience. It's always frustrating to have things happen that ruin a recordings.
If it's any consolation, you're not alone. Most of us were unsuccessful the first time out. Actually, most of us have had many failures before we learned all of the things NOT to do. It comes with the hobby and as you gain experience. you get better and better at making sure those things are taken care of ahead of time. Even though the weather was not in your control, we usually make the mistakes first and learn from them instead of anticipating and avoiding the mistakes in the first place.
That said, in my experience, there's really not alot that you can do to save a recording from really heavy rain. Light rain is no problem, but when it starts downpouring, I usually just pack it in even if I do have umbrellas, rain fly's etc.