@warren : The fluorescing plastics you mention are from specially designed lab plastics that floresce, so not related to polymer type or to everyday plastics.
FTIR and other spectrometry is notoriously difficult with marine plastics because they pick up so many other chemicals in water, so the spec profiles are usually different from library spectrums of virgin plastics. Chelsea Rochman at University of Toronto is working on a project to make a library of marine plastic spectrum profiles, but chances are that this won't be universal. Even with high-end equiptment, this is tricky. More citizen science methods to ID polymers are via relative density by floating them in water, salt water, oil, etc, and using burn tests and hot needle tests. To my knowledg, there's no comprehensive and validated forensic guide on that... something to work on for us!