This is what I was told, yesterday, via Direct Message, by Tesco's Twitter admin:
"Good morning,
Thank you for getting in touch.
I'm very sorry you've not been able to get any Cornflour in your local store. I understand how disappointing this was for you.
I can confirm these have now been discontinued. This appeas [sic] due to customer demand and won't be available in any of our stores.
I'm sorry that I can't be of anymore help at the moment and thanks again for taking the time to contact us.
Thanks - Michael"
Someone else was advised on 8 November:
twitter.com/rhodri/status/1591188626175455233