Not able to open InDesign file saved on a USB device

Did you try going to File> open recent? perhaps you saved it somewhere else. Are you on a Mac running Time Machine? if so, you may be in luck. I wouldn't blame your daughter, she was trying to help.

If your system is reading the USB drive, browse it and look for a file with the extension '.idlk'. Delete that file.

It's InDesign's "lock" file which normally only exists while a file is open. It is there to prevent two users from opening the same file simultaneously. The lock file would normally disappear when InDesign is shut down properly, but when InDesign crashes or is forced to close with a file open, the lock file remains and causes the error you're seeing.

And, as TSN advised, never work from/to a USB drive.

I'm getting the error message (after my daughter decided to close down my computer and re-start) EITHER THE FILE DOES NOTEXIST YOU DO NOT HAVE PERMISSION OR THE FILE MAY BE IN USE BY ANOTHER APPLICATION.

Did the USB drive mount after the restart?

Do not save onto USB, ever. Save onto your hard drive and COPY to the USB. They are notoriously unreliable. Also, MAKE BACKUPS. I can't say this often enough. YOU NEED BACKUPS.