some of my files in icloud drive disappeared. why? can i restore them?

See the article Access and manage your files in iCloud Drive - Apple Support

r files in iCloud Drive

iCloud Drive lets you access all of your documents securely from your iPhone, iPad, iPod touch, Mac and Windows PC.

When you sign in to iCloud, you'll have access to iCloud Drive. With iCloud Drive, you can keep files and folders up to date across all of your devices, share files and folders with friends, family members or colleagues, and more.

You can store files* in iCloud Drive as long as they're 50 GB or less in size and you don't exceed your iCloud storage limit. If you need more iCloud storage, you can upgrade to iCloud+. With iCloud+, you can also share iCloud storage with your family, without sharing your files. Find out more about prices in your region.

*Avoid storing app folders, libraries, .tmp, .vmdk, .vmware, .vbo

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Did you followed the article Change your Apple ID country or region - Apple Support when you left abroad , and carried your iPhone on the trip .