Keep in mind a calf doesn't neccessarily have to be scouring to be under attack by scour-causing bacteria or viruses. Some cause a lot of fluid loss by diarrhea, others cause very little fluid loss and manure looks normal -- but they're wreaking havoc on the calf's insides. Perhaps that was the inital problem, and while calf was not really "scouring", he sure didn't feel good enough to get up and nurse, and that could dehydrate him VERY rapidly.
If she still nursed last night I wouldn't give up quite yet. Try a shot of Vitamin B complex and electrolytes (what type are you using?) to stimulate her appetite. Might not be a bad idea to repeat the selenium (Bo-Se). I also give a standard shot of Vitamins A and D to any calf I'm treating - just figure they're losing lots of minerals, vitamins, and electrolytes when scouring.
You don't happen to have any IV fluids like lactated ringers or saline solution, do you? Some of that given SC with 5-10cc's of dextrose might give him the boost he needs.
Banamine and dexamethasone are two different drugs that can make the calf feel better and reduce inflammation in the gut. My vet says he's used Rally 20/Recover - it's an antihistamine - on scouring calves as well, in conjunction with dexamethasone and he likes the results. Can't vouch for it, myself, as I haven't tried it yet.
Calves don't really "forget" how to nurse off a bottle - if they won't nurse at one feeding when they drank fine before, it's because she they don't feel like it - just don't feel well enough to drink. I would guess that most likely you haven't whipped whatever bug is causing her trouble. So keep the calf on antibiotics. Nuflor's good. I'd go with something orally, too though, Spectam or SMZs. Make sure you keep plenty of fluids into that calf - even just tubing with water. Oh, and make sure you haul her to her feet and at least try to make her stand at least once a day. Good luck with her and hope she makes it for you.