In a non-destructive workflow, the image data is never modified. The image data checksum should never change. Rather, the edits are a kind of "edit list" stored in metadata, which can itself be optionally (separately) checksummed. If the metadata is corrupt, it can be discarded, effectively resetting the image back to its original pre-edit state. Yes, you'd lose the edits.
The location for metadata depends on the application. For DNG workflows, the metadata is a separate location in the DNG file, with separate metadata and data checksums. For other workflows, the metadata is in a sidecar (a per image file), or stored in a database managed by the application.
The location for metadata depends on the application. For DNG workflows, the metadata is a separate location in the DNG file, with separate metadata and data checksums. For other workflows, the metadata is in a sidecar (a per image file), or stored in a database managed by the application.