Recover deleted .SKETCH files
All file recovery software does the same thing: searches the disk for places where files are but the catalog says are free.

The single most important thing to do to ensure that you can recover an accidentally deleted file is recoverable is to do nothing to the HD. If it is the OS disk then just using the computer runs the risk of the OS writing to some or all of the space that the deleted file occupies.

So when you recover a file you should always recover it to another volume. As recovering to the same volume can be overwriting other files you may need to recover.

After a month I am surprised there was even 5MB left that was recoverable. If that was all the recovery software found and the files are not openable it is unlikely they ever will be.

The first time this happened to me I went out and bought a backup drive and software. It's a lot easier than file recovery.