If you are running Version 1.3 or higher (current version is 2,78) - another reason to keep your DTX up to date!), there is a backdoor method for recovering deleted test results. Power down the DTX. Hold down keys F1 and EXIT. Power on the unit keeping these keys held down. Do not let go of the keys until you see the main screen. This will also work for the MMC so long as you did not use the Format option on the MMC.
Don't have Version the latest version or you formatted the card? If tests results are inadvertently deleted from the memory card, recovery may be possible. Fluke Networks can attempt to recover lost results off an MMC at no charge for Gold Customers.
The last MMC we recovered lost data contained MP3 (music) files.