What is the 'counterpart' of unprecedented?

I'm not looking for the literal antonym. Unprecedented means 'never seen/happened before then', but what is the word for 'never seen/happened since then'?

I have a feeling it might be unrepeated, but that doesn't really sound like an actual word.

The closest match I can come up with is never-to-be-repeated.

Though it's not easy to find defined as a lexeme, it's common on the internet.

A never to be repeated experience - Ennio Morricone plays his last ever Irish Concert. [facebook]

................

a never to be repeated special offer - Willis' Walkabouts [facebook]

................

CED has an example using the same string, but not as a premodifier:

This is an offer never to be repeated.

The term is not entirely well-defined, as it can carry either the 'it is not intended that this be repeated' or 'this was the last time it took place' sense.