We are using ProSeries Professional and are regularly having client files disappear.  I have been unable to replicate the issue directly, as it appears to happen at random after a file is updated, saved and closed.  Users are not deleting the file.  This is a network environment with ~12 users.

I'm running two backups a day so we've been able to recover our data, but I'm deeply concerned about what's going on here.  I've had to restore about a dozen files thus far and I'm convinced it's not user error.  We've been using ProSeries for roughly 20 years and never experienced file loss like this.  I've seen some other posts regarding file loss and wonder if something is happening at the software level.

I recommend checking your data files occasionally.  If you don't have a *.cache file and a *.21I file for each client, you may have experienced data loss and not know it.