Hi MJB and welcome.

Just to reinforce Amanda's question - as you say, the view into the enclosures is a facinating - and obvious - speculation if Silbaby was there at the time, yet neither Pollard nor Whittle mention Silbaby at all, despite spending so much time right next to it.
The obvious assumption is that they knew exactly what it was, and that it was an irrelevance, and we're barking up the wrong tree. Yet we still can't seem to find anything that indicates what it is.