So a friend's sprites almost all turned to the default icon. This is the second time it's happened and we're at a loss as to what the reason is. Has anyone dealt with a similar issue?
Were there any error messages when opening the game in the editor?
This may happen if there was a problem saving or loading the sprite package ("acsprset.spr" file). The project contains references to sprites, but if the "acsprset.spr" was not saved or loaded properly their actual images are lost, and these sprites will be temporarily displayed using a placeholder.
In theory there are two ways this may be fixed:
1) AGS creates a spritefile backup called "backup_acsprset.spr", if you rename it to "acsprset.spr", replacing broken file, this may revert latest save.
2) By doing "Replace sprite(s) from source" command from the context menu (may be used on multiple sprites at once); but this will work only if you still have source images at the same locations you imported them from (ideally - if they are also somewhere inside the game project folder). That of course may take a while of manual clicking if you need to restore alot of sprites.