Question Author
The canning line must have some basic food hygiene regulations in place and they must tell their employees what's acceptable behaviour and practice. Even if they allow they're employees to eat on the job, they must surely provide some means of disposing of such things as wrappers safely. It follows that a wrapper found in a sealed can can only have been put there deliberately.
I've worked for a supermarket myself and I know that the buyers inspect the canning lines to check on the likelihood of this sort of thing happening. If they think it could happen, they tell the manufacturer to stop food consumption on the production line or else.
Compensation? No. My teenage son almost threw the cooked product at his mother out of shock when he found the wrapper What I want to do is to allow the manufacturer to investigate the complaint so that this situation doesn't happen to another parent. I'd guess that you wouldn't want a similar encounter with your offspring and I'd remind you that despite this compensation culture prevalent in the UK, not everyone is out screw money out of retailers/manufacturers.
Finally, the can and wrapper went back to the retailer for them to investigate. They are looking into it and will write to me. What would be the point of jumping out and down in a trading standards office and reading about the supplier being fined thousands months later? I just want them to accept responsibility and do their utmost to ensure no one else has this experience.