If you are using Reforged world editor and didn't use it much since the time when your map was lost, there is a possibility of backups of your map getting created in the directory "Documents/Warcraft III/JassHelper/backups/" but it is a rolling backup I think, so probably the more you have opened and saved maps since the time when you lost your map, the less likely it is that there will be a backup in this folder. I'm also not certain what the rule is for when backups do and do not get created in this folder, although you could probably lookup the jasshelper documentation to find out.
Anyway, it is worth checking. Before any more time goes on, first thing I recommend is copy the "backups" folder in that location from your computer to some other place where you control it, just to be sure while you are going through this folder and reviewing in case your map is in there that you can make sure it doesn't write over it while you're looking through what was there. (Keep in mind, World Editor with JassHelper plugin would actively write over the stuff in that backups folder while running and saving anything)
The second place to check that is also unlikely but possible to contain a backup is the folder "C:\Users\<username>\AppData\Local\Temp\WorldEditTestMap.w3x" but this will only contain the most recently played map with the "Test Map" button in the World Editor, so if you tested any map, or the broken version of your map, then this will contain the broken version. Also, the folder "AppData" is a windows hidden folder so you'd have to google how to make those visible.
Edit: in the case if you are lucky, my advice would be:
- find the backup of your map that has the assets, but it's outdated
- get the new "good" but corrupted copy of your map that's missing the assets
- use an automated tool to dump all the assets into the good copy from the bad copy, so it's like a 1-click way to correct what's in the good copy. that way you don't lose your changes