From what I understand about orchids, if your species doesn't like bathing in water directly then it wouldn't take very well to being stuck directly into the wet sphagnum moss.
I snipped this part off, wrapped the raw end in a paper napkin, soaked it in distilled water and placed it in a baggie.
You'll want to remove the end of the orchid from the water as quickly as you can. Overnight may be too long to recover it but who knows... again, I don't know your species.
Gather together a few things and you could hopefully encourage your little orchid back.
-Gallon ziploc bag
-Rubber band or thick twine for tying
-Your poor little orchid!
Dry your orchid completely where it has been sitting in the water. If it has sat too long it will begin to rot and really you can't save it after that.
Wet down your moss, damp but not dripping wet. You want to encourage moisture in the air, not a sweat bath. Place the moss in the bottom of the gallon bag, position your orchid so that the cut end doesn't touch the wet moss but all the branches are above the bag.
Now, blow some air into the bag and seal up. This is tricky but you'll get it. It doesn't have to be perfect, just so there's enough air in the bag to support the orchid upright(-ish) and keep it from touching the moss or the sides of the bag where moisture tends to collect. You'll probably get seriously creative trying to keep your orchid upright anyways (I leaned mine against various cans of vegetables and a ziploc bag of sugar...).
Now, place your orchid and her new contraption in indirect sunlight and away from drafts or heaters. The rule of thumb about indirect sunlight that I follow is this: if you can see a fuzzy shadow when you put your hand in the location, this is good; if you see a sharp shadow, this is direct sunlight and not good.
Once a day or every other day, mix up a weak orchid fertilizer batch and soak the end in it for 30 min to an hour. Dry thoroughly and re-wrap with the plastic bag/moss contraption.
This method has worked exactly once in the five times I have accidentally killed an orchid. :/ I read about it in a book somewhere about raising orchids but really should have been called, "How to Perform Orchid CPR". Sometimes I think a harsh word and a loud bang will kill an orchid.
These plants are just too high-maintenance and sensitive for me but it sounds like you have an attachment to your little fella... best of luck!!
"A weed is a plant that has mastered every aspect of survival except for growing in rows." -Anonymous
"A society grows great when old men plant trees whose shade they know they shall never sit in." --Greek proverb