The Debian policy manual says:
"In addition, the copyright file must say where the upstream sources
(if any) were obtained, and should name the original authors."
This clause is made up of two requirements:
1. "the copyright file must say where the upstream sources ... were
obtained"
2. "the copyright file ... should name the original authors"
libstroke does not violate the first requirement: the copyright file
does say where the upstream sources /were/ obtained, even though they
can no longer be obtained there.