My mom was writing a text in Office Word and she wanted to save it on her USB flash drive. She says that the computer was trying to save it for a long time and then a text popped up (she didn't read it carefully and doesn't remember what it said) and in upper left corner, next to the document name, it said ''Not responding''. She closed the pop-up window and continued to write the text for approximately 20 minutes. During this period she continued saving the file over and over successfully and made a copy of it on desktop.
Then she tried searching for another file on the same USB flash drive. She opened a folder which should contain about 10 subfolders and some documents. The subfolders were all gone but one (she thinks it might have been a folder with an unknown name, but again she doesn't remember), but all the documents were there plus one unknown document (she says it looked like an autogenerated document).
Then she went to This PC where she found her USB flash drive but the bar which shows how much memory is left on it was red for the first time (there is only 1 GB left on the device). After that she pulled the USB device out of the computer.
Here comes the weird part. I've tried inserting the USB flash drive into three different computers and a smart TV afterwards. All of them recognized the device only for a couple of seconds. It was enough for me to see that the main folders are still there and I saw on Disk Management that there is 15 GB of memory saved on the device which is correct. Then I tried inserting the device into the same computer, but this time Disk Management said there is 15 GB of unallocated memory and the disk disappeared after a couple of seconds again. The third time, it didn't disappear and disk management showed the disk but it said that there was no media. That time the device also appeared in This PC section but there was no memory displayed beneath the name of the disk as it usually is.
It's a very important USB flash driveC because most of my mom's work is saved on it and she backed up only the most important documents so I don't dare to guess what to do because I'm afraid of losing the documents permanently.
What could be the reason why the USB device isn't recognized and how can I solve this problem?