My thoughts exactly. The only true way is to appear to have never been there forensically, leave no sort of evidence. Security through obscurity only works in some instances.
There was a murder in Nebraska where crime scene was liberally cleaned with bleach to obliterate DNA evidence. Still no conviction despite a lot of circumstantial evidence. This was partially compounded by older DNA technology that destroyed the sample while processing it.
For PCR you only need a super-tiny bit, then you can amplify it as much as you want. I guess you're still technically destroying that tiny bit, but it hardly makes a difference when you only need a few molecules.