There is probably not a lot we can help with now you have started on the restore of backups path, that is the ultimate solution to issues and outside the realm of a single plugin so to speak.
Hard to comment with absolute certainty what may have happened when you deleted BP – or did you just deactivate it? A white screen is suggestive of perhaps wp still trying to load the bp default theme, but speculation now is largely irrelevant.
Not sure why your hosts failed to restore your site from backups, or how your WP blog posts entries could have gone missing, only thing I can suggest is that you go back to your host and establish what level of site domain backups they keep, you may need to restore your site to a date preceding your activation of BP, also have you taken any DB backups yourself through something like the hosting account cPanel or Plesk control panel, simply restoring a DB dump/backup from a moment before BP should restore all your WP site and data.