Jesus! I hope the baby is OK now. I'd take him to the hospital anyway and make sure you inform the Area Manager at the Co-op as he will have to inform the HSE. I used to work for a large supermarket (in the supply chain) and know how there stock rotation isn't strictly adhered to. This is why I always shop from the back of the shelf 
The area manager should have informed HSE as soon as he had finished taking the OP's call.
Simple fact of life is.....
The minute any "manager" says to you "leave it with me and I'll get back to you".......that simply means "give me 24 hours to cover my arse and procure a £10 gift voucher, and I won't be telling anybody anything unless I really have to".
I hope you're little one is recovering. Good that it bounced really. If it was tainted, you wouldn't want it getting toofar into the digestive system.
Withe regard to the area manager comments, I'm sorry to disagree, but what's said above is pure speculation. From what was written, he certainly seems to be taking it seriously and frankly there was little else he could have said other than "I'll get back to you". He will need to check on the facts, whether that tin was a rogue out-of-date one, or whether there was a batch (there would need to be a recall) and so on. You can't honestly expect him to do anything else on the basis of the first phone call.
There are good managers and bad managers. Don't always assume you have a bad one. Human error is involved and if one politely points out the facts, you will receive recompense. If you are not satisfied at that stage, then you get the big guns out.
