Depends what's happened. Did they say why it was knackered? If you've run over a big piece of glass since the service then that'd do it, for example.
Am I being paranoid? Had a stage two service a month ago on my Brompton, asked the bike shop to look particularly at the tires and the chain, but got told everything was fine.
Then last week I got a puncture, and took the bike back to the same shop for an inner tube replacement* who then said the tire was seriously knackered and needed replacing.
I donít doubt the tire was past it but my concern is they didnít really do anything when it went in for servicing.
* Brompton tires are notoriously difficult to remove, best left to the professionals