It’s possible to lose something significant and not really notice.
I lost my pump about 6 months after getting the bike.
I heard something fall off and bounce along the road, but assumed it was a light - as that’s the usual culprit.
Checked my light and couldn’t find anything on the road.
Didn’t realise it was the pump till months later when I needed it.
I know exactly where it was (top end of Hyde Park) but can only assume that it bounced on the road and then up the kerb into the grass - which is why I couldn't see it at the time.
Didn’t bother replacing it with another Brompton specific one, I now carry one in my bag instead.