I believe I have encountered the same bug but as it happened I also lost all saved crafts here is the feedback I had written on discord :
"
After a failed launch attempt, I tried to resolve the issues and it wouldn't save the ship anymore. I thought okay not a big deal let's try to launch :
I tried to launch the rocket and the Launch button was unresponsive. I thought okay no biggie let's save the game :
esc -> save game -> gave it a name -> saved,
... or so I thought after relaunching the game it was back to a previews auto-save point.
And even after restarting the game it's impossible to launch or load previews crafts in the VAB.
I lost all of my craft, I haven't been playing for that long (5 hours) but it's quite scary.
"
