Followed by lots of appeal to annecdote ("I've heard similar things") and then the familiar one-way agnosticism ("How can we know?" "We need to treat everything as accurate until we can 'know'"...but only if it agrees with my contrary position). Notice this benefit of the doubt is only ever given to the "non-official" source.
The idea that this facebook post should be taken in any way seriously because it "looks credible" is ridiculous. Ditto the idea that there should be a glaring mistake in the post if the writer was faking it.
Also, not doubting something because you haven't interviewed several other people from the same field is insane. By this logic, if I made an anonymous post on facebook saying how staff at my nuclear power plant were covering up fractures in the fuel rods by doctoring x-rays you would have to believe me, or at least "leave it open", until you interviewed other people working at nuclear plants.
It always strikes me as strange, given how a large proportion of the NHS staff despise the Tories, if this sort of fiddling was going on, and was so widespread, you would expect to see a torrent of these posts, anonymous or otherwise.