Death of yesterday - M. C. Beaton

A dead witness. A forgotten crime. Hamish Macbeth never had it so hard as in this newest Highlands mystery!

Morag Merrilea is working at the Shopmark Fashions factory during her summer holidays to earn some extra cash.
But when the art student complains to Hamish about the theft of her sketchbook in the pub, he doesn't take her too seriously.
After all, she had been drinking and can't quite remember what happened...
and then turns out to be snippy when Hamish questions her further.

But then her body is discovered -- and Hamish is forced to investigate a crime where the only witness has been murdered . . .