That's a sad story all right - but it does sound like it was sick to begin with. Dehydration is a big issue with young birds. When i picked up the baby sparrow it drank & drank. I used a straw with one end cut like a spoon & closed off the other end with my finger to hold the water until I offered it. They are pretty smart & will adapt quite quickly.
You will see in the Dove & Pigeon forum some advice on helping a baby survive.
We also have threads on Megabateria etc. There are products listed in the 1st link that can be good to have in your medicine cabinet or fridge. Well worth a read.
Megbacteria
&
Megabacteria-one year later E Coli in parrots!!!!!