COVID antibodies

[littlequestion]

I had an antibody test (thanks to another thread on here). It came back positive.

The email said it's likely I had COVID in the last 6 months. I actually had symptoms 15 months ago, just before the first lockdown.

In the last 6 months I've been incredibly careful about meeting people (though kids were at school when it was open), had no symptoms and had my first jab early March. I've now had both.

My question is - is it likely I would still have had antibodies from an infection early last year or is it more likely I actually somehow caught it more recently?

PS if I were doing this research I would have asked participants if they had had a positive PCR test and if so, when. Then they could plot a curve of what % of people still have antibodies against time since infection. I would have thought that would be v. useful for scoping the appropriate timing for boosters

Zoe app did ask for this information, as did the NHS link when ordering it.
Had to say if and when you'd tested positive on pcr, if you had symptoms, if you'd been a close contact (household) of someone who had confirmed covid, etc.