I hope he's alright now. In this below information will help your friend to have insurance in the UAE while his on visit visa. Dubai already issue a decree Back in 2008 regarding health insurance for visit visa personnel, but I think many of us are not familiar.Here it is:
The Visitor Health Travel Insurance not only protects your visiting friends and relatives, it is also mandatory as per the Ministerial Decision No. 322/2008
I'm not promoting this insurance company but as an example you can check there payment plan, its very affordable for only 100 dirhams you'll have your premium health insurance in the UAE.Below is the link: Oman Insurance Company
I hope this information will help your friend and others too.