Parked in a Tesco car park but did not get a ticketWatch
And if you weren't fined at the time, its very unlikely anything further will happen.
Just forget about it.
If you didn't get a fine card put on your windscreen, then you should be okay.
I know this sounds like a stupid question but were you actually in the Tesco?
Some small inner town/city supermarkets run this system though, and I never noticed and never got told off for it!
If you didn't get a notice on your windscreen when you came back to your car I think you can safely assume that you're fine.
I don't drive but I think the general rule is if it's a private car park, you don't need to pay the fine. At least, that's what my family and my sister's in-laws do and they all get away with it every time.