ok here is how to reproduce the no widget scenario.
start at runway
change weather to few clouds (does not matter)
set wind 40 degrees off runway (again probably does not matter)
esc
save/load flt file
save to PC
resume
take off
fly
esc
restart
when you return all your widgets are gone - and there was usually a fly now button, but is not there.
Loading a flt file does the same.