Sometimes your antiviras will delete files, make sure it is set to ask you if you want to delete or clean. Goodluck
Maybe you already do this, just a suggestion; keep your embroidery files in a separate folder on your external drive. If you opened the files maybe you were just looking at a copy, and they can still be retrieved by searching your C: drive.
If you lost the designs and do not know why, most likely they are hiding. You either sent them to the wrong place or hit a key by mistake. Oh heck, the computer could have messed up, who knows! Just asked someone that you know that is computer savy to help you. You may have misplaced them instead of losing them. I call my son so I have an advantage and he usually tells me what to do. That is, if he has time! Just do not delete or clean out you trash file until you check it. Sometimes they can even be retrieved but not all of the time if you did delete them. You need to back up everything on a CD just in case. I go desktop, floppy disk(sewing machine will take a floppy disc), and then a CD. You never know when the computer will die! Good Luck!