Quoting norah's.momma✿:" So I took DD to a children's hospital in December because she had white stool and was just super sick, ... [snip!] ... Why would they do that? Plus they also sent me a BILL saying she didn't have insurance at the time, which SHE DID! Ugh"
They can rebill insurance. Don't sweat it. Just call the billing department and give them your insurance information.
I can't believe they would have given you a diagnosis of RSV in a letter. If she had RSV, she would have had to been treated for it. Did you read the letter wrong? Did it say that they ruled out the diagnosis of RSV?