Actually, I was able to locate my files in the .trash subfolders of my vault. Somehow they were not showing up in the search results. My apologies, I must have been doing something wrong.
Interestingly the problem is now somehow reversed. The deleted files are moved to the Obsidian vault’s .trash folder, EITHER when selecting ‘Move to system trash’ or ‘Move to Obsidian trash (.trash)’
To be honest this is not a problem for me anymore, since I now know where to look for deleted files.