Hi, as I understand it, you get 'false hypos' for two reasons.
The first is, as others have said, if your BG has been running high, and takes a step down.
The second is if your BG drops sharply, due to something like exercise, leaving you with suddenly lower than usual BG.
Sounds like both of these may have happened with you.
You can get hypo symptoms (which can be very unpleasant) even if your BG stays above 5.
You can also not get hypo symptoms at lower than 4 (non diabetics often go under 4 with no problems at all).
Personally, I dislike the term 'false hypo' because it suggests that the experience isn't genuine.
I much prefer a phrase I have seen used in American terminology; 'relative hypoglycaemia' which actually describes it much better.