When Lindsay picks up the wad of cash from the purse the top bill is a $100 but when Stella picks it up the top bill is now a $20.
When Stella hoses down the inside of the martini glass, she is actually diluting whatever trace was there. This makes it difficult to test for anything. If she is looking for diatoms, there will be two different types, unless the sprayer solution is made of distilled water, which has no diatoms. Again, there are problems when looking for anything, even under the microscope.