I wondered whether it would have been possible for the house to be owned and converted by a private trust. I'm sure it is possible to structure things so that a member of the public cannot figure out who to send the legal stuff to. Obviously, if it's a private individual, they just track you down and start legal proceedings.
Then there is the second option of "putting it back, as was" which I assume would require no permission and then applying for a change of use at a later date.
If I recall rightly, it went for £20k, which isn't very much money, In 20 years, it will have probably hit the £150k mark in real terms, which probably made it a good punt.
I reckon something along the offshore/trust route was probably the way to go for getting around the clawback. Then you have to also assume that the original party has access to the funding which would be required to start proceedings.....
It would have been an interesting thing to test.