This is a scam where your friend’s email account has been hacked and an email then sent to you stating that s/he is in trouble on vacation and could you send them a couple of thousand to help him/her out? If you get any emails like this, check that they have actually gone on holiday first!
If this has happened, tell your friend that his/her account might have been hacked. The hacker may have deleted all sent emails so it may not be obvious to them that there was a problem. They will need to change their password straight away and maybe enable 2-step verification.