Should have been scratched?

[Pedigree Ann]

Watching Fair Grounds races. In the second, a well-regarded (7/2) firster became upset behind the gate, backing up and sideways, then fell down hard on his side while the jock stepped off. Didn't see if the track vet even had a look at him; they put the jock up, shoved him in the gate, and dispatched the field. The faller broke poorly, made a bit of a move on the turn and flattened, looked a bit mentally distressed in the stretch. But should he have been in the race in the first place? Surely a horse who falls over needs to be thoroughly checked over to be certain it hasn't cracked a rib or something. Or am I making too much of the incident?