Can you please let us know if any of the below workarounds help:
1. On refreshing the contents of the folder (where these indesign files and idml are saved), the icons of indd and idml files should appear again
2. On the 2nd launch of InDesign the folder icons should reappear.
An error occurred while saving the commentAdam Doyle commented
This is ridiculous Adobe. We are all having this problem for it looks like a month now and you have no resolve? We need this white icon issue fixed please.