d'oh! I'll email him to see if he can still pick it up or find out where it has gone to.

Edit:
I've just emailed Hossein advising that the money has been paid out to the paypal address he originally provided, but had later asked us not to. I'm not sure the reason for the change of mind.

I've asked if his friend has received the money and can send it to Hossein, or else if his friend can refuse the transfer and then we'll get it back and send it to Hossein directly.

If the paypal address is wrong it may have gone to no-one or it may have gone to someone we don't know. We'll figure out the next steps once we're clear what the situation is.