When installed debian with LVM, using whole disk (default option), the LVM
was created on /dev/vda5, which was on vda2 extended partition:
Device Boot Start End #sectors Id System
/dev/vda1 * 2048 499711 497664 83 Linux
/dev/vda2 501758 41943039 41441282 5 Extended
/dev/vda3 0 - 0 0 Empty
/dev/vda4 0 - 0 0 Empty
/dev/vda5 501760 41943039 41441280 8e Linux LVM
when booted on bigger virtual disk, the primary partition 2 was changed to
type linux, containing the rest of the disk, which unfortunately made the
LVM unreadable.
the growpart should aparently support extended partitions...