For anybody who is losing samples often.
I use a 15" 2019 mac book pro, running OSX 10.14.2
For a while native access was consistently losing my samples, causing me to re download all of the VDL files. I could not find an answer for my problems anywhere online so I figured I would post the solution I found here.
One issue apple has is almost always downloading major files to the cloud instead of to the computer. When you download the VDL files, navigate to the download location and insure the "Virtual Drumline" file is downloaded to the computer by looking for a small cloud image next to the file name. See the attached images for the small cloud.
If you are unsure please post a question below.