I know how it feels to lose one.
Deer can be amazingly tough critters. I've seen them take some pretty serious wounds and still make it.
2 years ago, during bow season, I killed a doe that proves my point; I chose to shoot this doe because she had a broken front leg (had to wait for a healthy doe to get out from in between and a fawn to get out from behind before I could shoot). It was a perfect broadside double lung shot at 15 yards. I watched her run out into a bean field about 100 yards and fall over.
I tracked her even tho I saw her fall and found hair at the site and my arrow beyond. There was NO BLOOD until 10 feet before the deer. One drop! All the blood stayed inside the chest cavity. Weird stuff happens.
A couple of weeks earlier my buddy shot a doe and broke her leg. I'm pretty sure it was the same one.
When I skinned her out 4 buckshot pellets were under the hide on her neck. Don't know where that came from. Buckshot ain't legal here!
A year earlier my nephew hit a doe high in the back with his 20ga slug gun. We tracked her @ a mile and a half before we lost her. This doe had a healed over place on her back where 4 or 5 vertebra had fused together and one backstrap had a fist-size chunk that was just GONE! The other had a lot of scar tissue. Again, I think it was the same doe.
If I'm right, that means it took at least 4 hits to bring that deer down.
Maybe you hit yours a little to high in the back too. With luck she will recover and you'll get another chance at her later.
Good luck!
Did you find any hair? It can help figger out where you hit 'em.