Kitten death ?'s

I'm coordinating foster's in the area where I live and one of my new foster homes called tonight to tell me that one of the 10 wk old kittens had died very unexpectedly. The kittens were vaxed last Sat with a 3 in 1. On Wed they went to the vet and were spayed/neutered, they tested neg on a combo test. Their mother got very sick last week (she has been seperated from them for 2 weeks) and on Wed. was diagnosed with hepatitis, she also tested neg on a combo test. The kitten that died was eating, drinking and acting normal this morning before she left work, when she returned the kitten was dead by the bedroom door. The spay incision looks fine, the kitten has no signs of trauma and was kept in a bedroom seperate from the rest of her home. The only thing I can come up with is an embolism following the spay. Anyone else have ideas? Thanks!

It happens, in the best and in the worst of circumstances. You probably will never know what claimed the life of the kitten.