Well obviously this makes no sense! I have seen once before an apparent and unexpected loss of material. The only explanation then was that the tube must have been rattled during transfer to the freezer and some material 'jumped' into the recessed area of the cap, where it had frozen. When recovering the tube from the freezer, most of the material had apparently vanished but was recovered by warming the tube and microfuging. I hope the explanation is a simple as this, and that your DNA returns. The other explanation of course is that someone else has used it!

If you are using silica-based columns for extraction, it is very important to well dry columns (to eliminate ethanol traces) before elution. The presence of ethanol in your DNA suspension increases evaporation speed.

Definitely there is a error during conduct of the experiment leading to spillage or loss of sample DNA