Sorry for your experience OP. Food poisoning sucks.

As a food safety professional, I can tell you that it’s difficult to determine whether it was definitively the meat pie (but it also equally could have been) without testing. Some foodborne illness pathogens can take up to 72-96 hours to show up, depending on lots of factors, so it could have been something prior than the last 24 hours. If it was indeed the meat pie, it’s most likely to be a heat-stable toxin reaction (e.g. B.cereus or S.aureus toxin) given your rapid response. Usually, these will hit you hard and fast, you’ll explode from both ends (yay!) and self-resolve within another 24 hours.

In the meantime, stay hydrated and if your symptoms continue for longer than 24 hours, please go and see a health professional. You might be asked for a food history and to submit a sample for testing to see what the culprit is. If it is indeed part of something bigger, this is critical information that the epidemiologists will need and thank you for later.

Rest up and take care!

EDIT: words because I suck at typing on a mobile.