InCopy .icma files randomly hidden on Mac

We run a magazine and our editorial team uses InCopy to edit the text that designers set up in InDesign. We are all remote and use Synology to sync files between our office server and everyone's computers. Everyone uses Macs, though of varing models/ OS.

One of our editors today found that some of the .icma files were missing. Thinking it was a sync issue, we tried dropping a file into the folder and thats how we discovered it was hidden, not unsynced. By hitting [Command + Shift + .] she could see them again and open/use the file as normal. 

It's not ALL the .icma files, only some of them. All of the .icml files are still visible as normal. Different designers created them originally. Resaving the .icma and forcing Synology to resync them made no difference. The file names of the affected files are consistent with our naming convention so nothing out of the ordinary. Her Mac OS is Sonoma v. 14.3.1. This has not happened to her before, but it HAS happened to another editor in the past (using a different machine/OS).

tl;dr: Some .icma files were randomly hidden on a Mac laptop. After unhiding, they are still accessible. No apparent correlation between anything.

Has anyone else experienced this? Are there any remedies or explanations?