The body of the API response should contain an OperationOutcome resource with those details in it. Depending on what client library you're using, you might need to parse that response - the GCP client libraries are somewhat generic and don't know that they should expect a FHIR resource with error details. I used curl to check these examples.
If you got that Patient resource from a BlueButton server, the server is definitely not conformant. That's not just a profile issue - it's not valid FHIR at all.
When I try to execute the attached sample bundle with the EOB, this is the API response:
{
"issue": [
{
"code": "value",
"details": {
"text": "reference_not_found"
},
"diagnostics": "reference target(s) not found: Coverage/part-a--10000010254618",
"severity": "error"
}
],
"resourceType": "OperationOutcome"
}