This is a difficult one.
Personally, I don't even like the idea of 2 year servicing on cars, and at least do an oil and filter change yearly, unless very low mileage had been driven.
Yes, modern oils, and engine tollerances are far better better now days, but I would also argue that the first service is one of the most important. Any swarf or debris from manufacturering and the engine running in needs to be flushed out.
If it'd been 4 years, but only covered 2k miles, then maybe not a big deal, but the fact its double the time and 50% over the recommended mileage, I think would put a lot of people off.
However, it's VERY unlikely that it has caused significant damage, but there is no way of knowing.
No inspection can tell you this either, unless your gonna start stripping components.
I would say, your biggest issue would be re-sale. You'll be narrowing down your audience quite a bit, as most buyers of these sorts of cars prioritise mileage and service history when looking.
So..... You've got to decide personally whether it bothers you.
Have you checked with the dealer network whether it has actually missed the service and not just missing a stamp in the book?
Was the service that was carried out, a late 2 year service or an actual 4 year service? As the 4 year service includes more and can be significantly more expensive.
To get the service history back on track, it would be due another service in 2021 as well, is this being carried out prior to purchase?
Is the car priced low enough to take the service history into consideration?
Do you intend to keep the car a long time? If so, it will have much less impact, as your (on time) service history builds up and hopefully no issues arise.
Regardless of whether its this one or not, get an independent inspection done by someone recommended on here, as there are lots specific things to check that could negotiate you a better purchase price or save you a headache down the line.
