Unfortunately this currently can't be fixed on some systems as BTT can't influence when the bar is hidden by macOS and is not notified about it either. It seems to work on most systems with the latest versions though, but there still seem to be timing issues on a few systems.
I recommend to set a keyboard shortcut in BTT to quickly show/hide the bar. 3.280 will add some more checks but I don't believe they change much.
Your issue sounds quite weird though, I have not had other reports where it would have been hidden after screen saver. Maybe you could try to completely reset BTT by deleting ~/Library/Application Support/BetterTouchTool. Or possibly go to Help => Export Diagnostic Debug information and send it to andreas@folivora.ai, then I'll have a look at the logs!