Given the curry tends to get demolished by the first 4 or 5 CE rows, and is presumably batched out over numerous flights, you'd expect a lot of reported cases if there was a problem with food hygiene. I know that reheated rice is one of those enormous public health bugbears, and the BA meal will have the jerking knee of NHS blame pointed at it, but it would be extremely unusual if BA were not working within extremely carefully planned tolerances on food safety. It may be worth reporting if you haven't already, in case there are other occurences, and it might be worth thinking back to anything you ate in Venice.

Horrible thing to happen though, wherever it came from. At least it was after the homeward travel that the issues (so to speak) started, nothing worse than being abroad with stomach trouble.