If Scott's work visa ran out in May, it would suggest that his contract with the Devils, for work purposes, also ended then. His study visa information should have taken him until the end of his course. If the Devils had no work for him or did not intend to re-sign him, technically they have no further employment responsibility towards him - they had no obligation to ring up to get his work visa extended because he would not have been working for the organisation after May. With changes in immigration law, he would have had to provide the authorities with hard evidence (job offer, contract, evidence of company registered as trading) of any new UK employer he was going to be working for between May and September - if he couldn't do that, his work visa would not have been extended. This applies to foreign nationals already over here or coming to this country.
The Devils organisation was absolutely right if they told him he could only re-enter on a tourist visa after May because he might not be working for anyone by then. It would have been up to him then to check out the consequences/conditions and extension procedure for visas after that time.
No disrespect meant to Scott but he did show a little naievity a couple of months ago when he advertised on this forum that he and his girlfriend were looking for jobs over the Summer in the UK without a work visa. As with most countries now, anyone looking for work must have a valid work visa and be eligible - I'm sure this applies in the USA too. Let's face it,you simply can't get away with something like that without endangering the company you are working for and yourself as an individual!