OMG!! This question revives a nightmare situation we endured a couple of years ago.
S received a somewhat last minute fellowship offer to study in France for the next academic year shortly before he graduated from college. At the same time, he was offered a summer job in France helping to lead a language immersion tour. There was a huge rush to get everything done, and he left for the year 10 days after getting home. He had studied in France for a term earlier on, and didn’t need any kind of special visa, and apparently no one at the college mentioned the need for a long stay visa to him. So off he went. He worked in France for a while, then traveled to visit relatives in England and Ireland. When he re entered France, no problem, but when he showed up at the university in Lyons, they informed him that he needed a Long Stay Student Visa in order to stay in the country past 90 days and in order to get the Work Visa required for them to place him in the English teaching assistant job that was supposed to support him (tuition and room was covered, but nothing else). His Dartmouth professors had just told him he would get the work visa in France. Oy!
The bureaucracy was incredible. We tried appealing to the US Embassy for assistance: no dice. We contacted our Senator’s office and they tried: no dice. We contacted Dartmouth and they tried: no dice. We had to fly him back to apply for a visa in Boston, the nearest consulate, period. We had to go through Campus France, the whole deal. (The upside was that because of the time of year it was much faster than they indicated. That will not be the case for your S, most likely. 
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As you know if you have contacted a consulate, they insist that you go through their website and will not talk to you. I made an appointment for him at 10AM on a Monday in October, the earliest safe appointment for the period he would be home, which was scheduled to coincide with a school vacation there so that he would miss the fewest number of classes. You’ll never guess what happened next…
S had to take the Amtrak train to Boston that morning to be absolutely certain of arriving in time for his appointment. He had to leave the house at 4AM. On Sunday, it became clear that something else was going to be arriving in Boston that morning: Hurricane Sandy. Everything in Boston was closing in anticipation. Would the consulate close? Would they deign to give him another appointment? He had a plane ticket just over two weeks out, the amount of time they said it would take to get the visa. He had an appointment to take the GRE the next day in Lyons, the only day he could take it there. The consulate said nothing on their website. Finally, in desperation, I called their emergency contact number. A very irritated diplomat informed me that OF COURSE they would be open on Monday morning.
H took S to the train at 4AM. Unfortunately, I slept through it, so he left without a cell phone (I intended to give him mine, since his could only be used in France.) or a raincoat (I intended to have him take my father’s Burberry, which both of us can wear), and with only $25 in his pocket (I had $100 I was planning to give him, just in case). I don’t know what H was thinking. Anyway, he arrived in time for his appointment, and they shut the consulate as soon as he was done. (I guess all of the other people with appointments were stone out of luck, even if they traveled for hours to get there.) He immediately headed for South Station, where he got on the last Amtrak train heading north out of Boston…
Which stopped about 45 minutes north of the city. Wires blown down onto the track in NH. Amtrak trying to hire buses to take passengers north…Governor closes the Maine Turnpike…after 4 hours on the train, they back up all the way to North Station and disgorge the passengers. Meanwhile, all public transportation in Boston has been shut down. S is now stranded with about $10 in his pocket, no phone, and no credit or debit cards that will work in this country. He calls from pay phone. We discover that one can no longer call a pay phone in North Station back, probably for security reasons. I have a good friend who S knows who lives in Somerville. I contact her, he calls back and I give him her home #, he calls her. At this point he is running out of money. He hails cab–hallelujah!–and heads to her house. Cab driver gets lost and racks up $50 fare. She pays it. He is soaked to the skin, wearing nice tweed jacket, pants, silk tie, etc that they require for consulate appt. An umbrella isn’t much use in a hurricane.
To be continued…
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