Hi @ben85485 ,
The laptop is supplying the power at its end for its USB controller to work whereas with a flashdrive, because it has no internal power supply it relies on power being supplied to it from the USB port that it is plugged into, so the flashdrive's USB controller can operate and "talk" to the controller in the keyboard or whatever device it is plugged into.
You may be able to "see" the keyboard files when using the Windows File Explorer program in the laptop. The keyboard would show as a new drive letter and it would have files associated with it.
I don't know what the files would be called perhaps you may recognize the file names.
If you can find the files it's just a matter of "copy and paste" them to a remembered location on the storage drive (My Music folder for example) in the laptop. If you "cut and paste" or drag them it will remove them from the keyboard so be careful that if you do it this way to clear the storage in the keyboard, that you select the correct ones as you may erase the keyboard's operating files