I understand, because I too have been through the whole routine.
The DNA tests are not very informative on mucus, unless they give sequences to known disease causing organisms within it. Otherwise it will just read out a mixed bag of activated primers.
I usually check these artifacts for animal cellular patterns, or, unusual single-cell organisms surrounded by antibody accumulation caught within the matrix(microscopically).
I have found the "waste material" from helminths before, which has mucus membrane containing digestive material in sections. This is similar to fish waste.