Diablo 1 HD Hellfire Mod | Awake

Two of my characters got deleted, one at a time, and each time with them the current contents of my trade chest. The items on the other characters and in their individual stashes remained. I've then deleted the whole Belzebub mod and Diablo game yesterday, after my two highest characters (level 42 & 45) got erased.

Is this issue known? Is there something I can do to prevent this from happening or to reverse it? I'd like to know, before I start anew.

This has never happened to me. I have 3 characters (level 40, 40, 37) with a multitude of items in all chests. But I have to admit, I make manual backups of my saves every now and then. That's the best advice I can give you. And from now on, I think I'll also double the frequency of creating those backups.

Where are the save files located? Are those the files inside the c:\Diablo\Data\game_data & c:\Diablo\Data\player_save folders?

The save files are named "playerX". X being the number of creation starting from 0 (e.g. u have 2 chars, "player0" is the first char you created "player1" the second and so on) and the "treasure" file which represents the storage which every of your chars has access to. Both are located in the install directory under the folder data or save? (Duno exactly, but there are 2 folders inside the install directory one of em contains the save files).