The files are probably saved to a virtual image of the SD card. In order to actually get them written to the card, you would have to tell the operating system to unmount, eject or otherwise remove the SD card before physically removing it. Usually a restart or shutdown will do the same thing. The operating system will then write the image to the SD card, and if it is not doing a restart or shutdown, may tell you it is safe to remove the card.
This is done to increase the lifetime of the card. Every time you write to it, it wears out a little. Consequently, the system waits until you are done working with the file before doing the writing so it doesn't waste writes on stuff that will be edited right away.
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The files are probably saved to a virtual image of the SD card. In order to actually get them written to the card, you would have to tell the operating system to unmount, eject or otherwise remove the SD card before physically removing it. Usually a restart or shutdown will do the same thing. The operating system will then write the image to the SD card, and if it is not doing a restart or shutdown, may tell you it is safe to remove the card.
This is done to increase the lifetime of the card. Every time you write to it, it wears out a little. Consequently, the system waits until you are done working with the file before doing the writing so it doesn't waste writes on stuff that will be edited right away.