You probably were, it is part of the mandatory course administered to children (at least it was/is in Central/Eastern Europe)

Building on this, the vaccination programmes of the EU countries have converged to the extent that I was able to vaccinate my 3 month old in accordance to the Swedish vaccination programme while on vacation in Portugal by just showing up at a health centre and asking for a vaccination in accordance to their vaccination programme.

They even use the same vaccines.

If you are younger than 30 you will have had a polio vaccine if you parents followed the national vaccine programme in any European country. If you are younger than 50 chances are that you have been vaccinated as well.

Turns out I didn't remember it because it's part of those combined vaccines. I hope my immune memory is better than my cerebral.

You can get an adult booster. I was a recipient of pink sugar cube, possibly Salk vaccine in the 60s. I got a booster with my son's series in the 90s.

Don’t you have a vaccination record /pass in which all childhood vaccinations are recorded? https://en.m.wikipedia.org/wiki/International_Certificate_of...

You may have had a 'cocktail' shot:

https://www.cdc.gov/vaccines/parents/why-vaccinate/combinati...

At least in France it's combined with the tetanus one - I'd imagine it's the same in other countries too.

Boostrix-IPV https://www.medicines.org.uk/emc/files/pil.5302.pdf

That should be easy enough to sort out. Go to your GP and ask them about it, they should be able to make a booster shot happen.