If the crew have followed SOPs (and it sounds like they did) then no criticism at all. But if they were already sat in the aircraft when the situation was discovered by the crew, I wonder what the handling agent was doing .......
It's one thing to be unable to board passengers, because that can happen for a range of reasons, it's another to then make disabled passengers sleep on the airport floor.
Regarding "back office snafu", do Ryanair have any back office operations staff at all ? My own experience (FR flight cancelled due to snow) was that getting a refund required calling a phone number which was never, ever answered - oh, and we had most certainly NOT paid only £10 for the ticket.