Because they ticked "no" - they should have ticked "don't know" unless they knew how to identify it. Just give Paul Beckett a call on the number above and he will explain all.
Hi, though it's not my area, my company are one of the top national (and local) experts in this - www.phlorum.com.
If you call our office someone will be happy to talk through any queries you have for free. 01273 307167
They are also linked to a legal firm that deal specifically with this...