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These records probably cannot be restored. Am I correct that you open your file directly from drop box? I could be wrong, but I don't think Drop Box will upload a new copy of the file to "the cloud" while the file is open. Instead, it uploads once you close the file. Thus, any data added to the file since the last time that you closed it will be lost as Drop Box has not yet uploaded that copy of the file to its server.
You might find this method for saving regular copies of your file useful: Saving Sequential Back Ups During Development