Convective ("heat") thunderstorms are pretty much impossible to forecast precisely. On the day of, I'd recommend to use the radar, satellite and wind measurement, to get a picture what's happening, not the forecast anymore.

"Use the radar, satellite and wind measurement"

I did. And they showed me no clouds, rain or wind worth mentioning.

If you were in the storm.and the radar didn't show anhthing maybe the radar was out of service in that area, which is very unusual.

It's not realtime, some of the underlying models only get updated every 6 hours.