If I may be of assistance:
The Oxford English Dictionary definition of 'thought', in this context goes something like this:
an idea or mental picture, imagined and contemplated
As in cazatou's (K52's) quote:
The Investigating Board 'THOUGHT' that the aircraft WAS in cloud and NOT flying VFR when they made the waypoint change.
ie: An idea 'imagined' or 'contemplated'.
I can't fault their imagination, as long as it is left at only that.
HTH