My credit card issuer/bank held up a transaction I was making abroad why would they do this?

Your card company is probably using fraud-detection software that checks for unusual spending patterns on its customers' cards. If you don't normally use the card abroad the software will spot this and your transaction may be held up while the card company makes checks to see if the suspect transaction is genuine or not. If it isn't, an immediate block can be put on the card, stopping a fraudster from using it further.

Some card companies like their customers to advise them if they are going to be using their cards abroad. Whether you do this or not you should always keep a note of your card company's 24-hour contact number with you in case you need to speak to them in an emergency.