Beside the lake, beneath the trees, fluttering and dancing in the breeze. But not near the food in supermarkets. According to this report in the Guardian, Public Health England have issued guidance that says daffodils should not be displayed in shops near the food as daffodil bulbs are easily mistaken for onions, and daffodil stems look like a "type of vegetable popular in China". There seems to be no sign of this announcement on the Public Health England website, but however.
So, where is the evidence?
The Guardian quotes the British Columbia Drug and Poison Information Centre, a reputable looking site that also happens to be quite near the top of Google search results for daffodil poisoning. Slightly lower down the results is The Poison Garden, which has a lot of detail (the site is run by someone who volunteered at the Poison Garden at Alnwick Castle, but is not connected with it). There are plenty of stories of poisoning in this site, but as it points out, it is poisoning that usually does not require hospital treatment and so does not end up in statistics.
It seems not to end up in the medical literature either, for, I imagine, the same reason. A search of NICE Evidence Search for daffodil poisoning finds three things, one of which is a red herring. The first is about plant enquiries made to New Zealand's National Poisons Centre, reporting that the daffodil was the tenth most commonly reported plant. The third is from the Pharmaceutical Journal, providing historical stories about bulb poisoning. If you search NICE Evidence Search for just daffodils, you find items about contact dermatitis caused by daffodils, and galantamine, a drug used for treatment of cognitive impairment and Alzheimer's disease (and one of the compounds mentioned by The Poison Garden as causing problems if you eat the bulbs).
Searching Google for daffodil poisoning site:nhs.uk finds information from NHS Choices, covering plant dangers in the garden and countryside and making a tiny but significant mention of daffodils.
Looking in PubMed turns this up, an article about poisoning caused by eating the stalks. Although the study was published in an American journal, the incident involved the Chinese community in Bristol. The daffs were indeed next to the veg. This incident is mentioned in The Poison Garden.
So, where's the evidence and what is it? Not much in the peer reviewed literature, but some sites that advise of the problem and record the stories of individuals.