Exhaust

My partner took her car for its MOT last year and it failed on the emissions. She got it repaired and it then passed. This year she's taking it for its MOT and it failed on the emissions again. THe item that we got repaired last year should be just in warranty but we can't find the receipt. We know we took it between 28th March and 2nd April last year because the 28th was when it failed and the 2nd April was when it passed.

We've rung the garage we took it to to see if they had any records but because they had just re-opened they had no recards going beyond mid april.

Are we able to claim anything on the warranty?

Thanks

Simon