Belay your vet's orders!
By prescribing mineral oil, he disqualified himself as an iguana vet. He could not have made a worse mistake.
Because of iguanas' unique digestive systems, laxatives can be deadly.
Did he at least do an x-ray? Does it show anything?
Your iggy may have swallowed something that just can't fit inside his intestines. Like a large peach pit or a baby toy, or women's panties. Each incident did happen, with happy endings.
"Again, a vet visit and work-up will be required to determine the cause and initiate treatment. (Quote from anapsid.org)"
During this delay, feed him as much liquid water as he will take.