Who are you insured with? (I worked in car insurance for two years, there are, of course, different processes.)
- You need to tell your insurance company that you collided with the bollard.
- You also need to tell them that as far as you are aware, you didn't hit any Third Party vehicle. Since there's no footage of you doing it or not doing it, nothing can be proven unless there is either an independent witness who supports the Third Party's version of events, or an independent engineer inspects both your vehicle and the TP vehicle, and determines that their damage isn't consistent with your vehicle.
EDIT: Just saw your later comments. It's likely at this point that your Insurers will attempt to repudiate the claim as a case of mistaken identity, and it'll go away.
If there was damage to the bollard, however, and the staff member notified her superiors, Tesco would be able to claim for the damage from your Insurers (which goes down as a claim on your history).