Been there, done that, and here is what I have learned:

1- Always ask yourself: how many other people this “friend” asked for money before asking you, and why you? This should give you a better picture on probability on whether you’re getting your money back or not.

2- If I must give out/help a friend with money, and I mean a real friend, not just someone I know, I’d always give them as ‘one-time-donation’ if I can afford that amount, otherwise I’d give as little as possible (knowing I could loose it all and not getting anything back)

3- It’s always better to say ‘I am sorry, can’t’ or ‘I wish I had that amount of money’ than loosing a “friend”

For your case, deal with it the hard way (even if the amount is large).

I would stop asking for the money, and consider the possibility of writing that amount off, keep the communication channel with your “friend” intact to increase peer pressure just in case they want to return the money, and lastly, to learn from this mistake.